why global warming is real essay

What evidence exists that Earth is warming and that humans are the main cause?

We know the world is warming because people have been recording daily high and low temperatures at thousands of weather stations worldwide, over land and ocean, for many decades and, in some locations, for more than a century. When different teams of climate scientists in different agencies (e.g., NOAA and NASA) and in other countries (e.g., the U.K.’s Hadley Centre) average these data together, they all find essentially the same result: Earth’s average surface temperature has risen by about 1.8°F (1.0°C) since 1880. 

( bar chart ) Yearly temperature compared to the twentieth-century average from 1850–2023. Red bars mean warmer-than-average years; blue bars mean colder-than-average years. (line graph) Atmospheric carbon dioxide amounts: 1850-1958 from IAC , 1959-2023 from NOAA Global Monitoring Lab . NOAA Climate.gov graph, adapted from original by Dr. Howard Diamond (NOAA ARL).

In addition to our surface station data, we have many different lines of evidence that Earth is warming ( learn more ). Birds are migrating earlier, and their migration patterns are changing.  Lobsters  and  other marine species  are moving north. Plants are blooming earlier in the spring. Mountain glaciers are melting worldwide, and snow cover is declining in the Northern Hemisphere (Learn more  here  and  here ). Greenland’s ice sheet—which holds about 8 percent of Earth’s fresh water—is melting at an accelerating rate ( learn more ). Mean global sea level is rising ( learn more ). Arctic sea ice is declining rapidly in both thickness and extent ( learn more ).

The Greenland Ice Sheet lost mass again in 2020, but not as much as it did 2019. Adapted from the 2020 Arctic Report Card, this graph tracks Greenland mass loss measured by NASA's GRACE satellite missions since 2002. The background photo shows a glacier calving front in western Greenland, captured from an airplane during a NASA Operation IceBridge field campaign. Full story.

We know this warming is largely caused by human activities because the key role that carbon dioxide plays in maintaining Earth’s natural greenhouse effect has been understood since the mid-1800s. Unless it is offset by some equally large cooling influence, more atmospheric carbon dioxide will lead to warmer surface temperatures. Since 1800, the amount of carbon dioxide in the atmosphere  has increased  from about 280 parts per million to 410 ppm in 2019. We know from both its rapid increase and its isotopic “fingerprint” that the source of this new carbon dioxide is fossil fuels, and not natural sources like forest fires, volcanoes, or outgassing from the ocean.

Philip James de Loutherbourg's 1801 painting, Coalbrookdale by Night , came to symbolize the start of the Industrial Revolution, when humans began to harness the power of fossil fuels—and to contribute significantly to Earth's atmospheric greenhouse gas composition. Image from Wikipedia .

Finally, no other known climate influences have changed enough to account for the observed warming trend. Taken together, these and other lines of evidence point squarely to human activities as the cause of recent global warming.

USGCRP (2017). Climate Science Special Report: Fourth National Climate Assessment, Volume 1 [Wuebbles, D.J., D.W. Fahey, K.A. Hibbard, D.J. Dokken, B.C. Stewart, and T.K. Maycock (eds.)]. U.S. Global Change Research Program, Washington, DC, USA, 470 pp, doi:  10.7930/J0J964J6 .

National Fish, Wildlife, and Plants Climate Adaptation Partnership (2012):  National Fish, Wildlife, and Plants Climate Adaptation Strategy . Association of Fish and Wildlife Agencies, Council on Environmental Quality, Great Lakes Indian Fish and Wildlife Commission, National Oceanic and Atmospheric Administration, and U.S. Fish and Wildlife Service. Washington, D.C. DOI: 10.3996/082012-FWSReport-1

IPCC (2019). Summary for Policymakers. In: IPCC Special Report on the Ocean and Cryosphere in a Changing Climate. [H.-O. Pörtner, D.C. Roberts, V. Masson-Delmotte, P. Zhai, M. Tignor, E. Poloczanska, K. Mintenbeck, A. Alegría, M. Nicolai, A. Okem, J. Petzold, B. Rama, N.M. Weyer (eds.)]. In press.

NASA JPL: "Consensus: 97% of climate scientists agree."  Global Climate Change . A website at NASA's Jet Propulsion Laboratory (climate.nasa.gov/scientific-consensus). (Accessed July 2013.)

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How did we get here the roots and impacts of the climate crisis.

People’s heavy reliance on fossil fuels and the cutting down of carbon-storing forests have transformed global climate.

For more than a century, researchers have honed their methods for measuring the impacts of human actions on Earth's atmosphere.

Sam Falconer

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By Alexandra Witze

March 10, 2022 at 11:00 am

Even in a world increasingly battered by weather extremes, the summer 2021 heat wave in the Pacific Northwest stood out. For several days in late June, cities such as Vancouver, Portland and Seattle baked in record temperatures that killed hundreds of people. On June 29, Lytton, a village in British Columbia, set an all-time heat record for Canada, at 121° Fahrenheit (49.6° Celsius); the next day, the village was incinerated by a wildfire.

Within a week, an international group of scientists had analyzed this extreme heat and concluded it would have been virtually impossible without climate change caused by humans. The planet’s average surface temperature has risen by at least 1.1 degrees Celsius since preindustrial levels of 1850–1900. The reason: People are loading the atmosphere with heat-trapping gases produced during the burning of fossil fuels, such as coal and gas, and from cutting down forests.

To celebrate our 100th anniversary, we’re highlighting some of the biggest advances in science over the last century. To see more from the series, visit Century of Science .

A little over 1 degree of warming may not sound like a lot. But it has already been enough to fundamentally transform how energy flows around the planet. The pace of change is accelerating, and the consequences are everywhere. Ice sheets in Greenland and Antarctica are melting, raising sea levels and flooding low-lying island nations and coastal cities. Drought is parching farmlands and the rivers that feed them. Wildfires are raging. Rains are becoming more intense, and weather patterns are shifting .

The roots of understanding this climate emergency trace back more than a century and a half. But it wasn’t until the 1950s that scientists began the detailed measurements of atmospheric carbon dioxide that would prove how much carbon is pouring from human activities. Beginning in the 1960s, researchers started developing comprehensive computer models that now illuminate the severity of the changes ahead.

Today we know that climate change and its consequences are real, and we are responsible. The emissions that people have been putting into the air for centuries — the emissions that made long-distance travel, economic growth and our material lives possible — have put us squarely on a warming trajectory . Only drastic cuts in carbon emissions, backed by collective global will, can make a significant difference.

“What’s happening to the planet is not routine,” says Ralph Keeling, a geochemist at the Scripps Institution of Oceanography in La Jolla, Calif. “We’re in a planetary crisis.”

Setting the stage

One day in the 1850s, Eunice Newton Foote, an amateur scientist and a women’s rights activist living in upstate New York, put two glass jars in sunlight. One contained regular air — a mix of nitrogen, oxygen and other gases including carbon dioxide — while the other contained just carbon dioxide. Both had thermometers in them. As the sun’s rays beat down, Foote observed that the jar of CO 2 alone heated up more quickly, and was slower to cool down, than the one containing plain air.

The results prompted Foote to muse on the relationship between CO 2 , the planet and heat. “An atmosphere of that gas would give to our earth a high temperature,” she wrote in an 1856 paper summarizing her findings .

Three years later, working independently and apparently unaware of Foote’s discovery, Irish physicist John Tyndall showed the same basic idea in more detail. With a set of pipes and devices to study the transmission of heat, he found that CO 2 gas, as well as water vapor, absorbed more heat than air alone. He argued that such gases would trap heat in Earth’s atmosphere, much as panes of glass trap heat in a greenhouse, and thus modulate climate.

Today Tyndall is widely credited with the discovery of how what we now call greenhouse gases heat the planet, earning him a prominent place in the history of climate science. Foote faded into relative obscurity — partly because of her gender, partly because her measurements were less sensitive. Yet their findings helped kick off broader scientific exploration of how the composition of gases in Earth’s atmosphere affects global temperatures.

Heat-trapping gases 

In 1859, John Tyndall used this apparatus to study how various gases trap heat. He sent infrared radiation through a tube filled with gas and measured the resulting temperature changes. Carbon dioxide and water vapor, he showed, absorb more heat than air does.

Carbon floods in

Humans began substantially affecting the atmosphere around the turn of the 19th century, when the Industrial Revolution took off in Britain. Factories burned tons of coal; fueled by fossil fuels, the steam engine revolutionized transportation and other industries. Since then, fossil fuels including oil and natural gas have been harnessed to drive a global economy. All these activities belch gases into the air.

Yet Swedish physical chemist Svante Arrhenius wasn’t worried about the Industrial Revolution when he began thinking in the late 1800s about changes in atmospheric CO 2 levels. He was instead curious about ice ages — including whether a decrease in volcanic eruptions, which can put carbon dioxide into the atmosphere, would lead to a future ice age. Bored and lonely in the wake of a divorce, Arrhenius set himself to months of laborious calculations involving moisture and heat transport in the atmosphere at different zones of latitude. In 1896, he reported that halving the amount of CO 2 in the atmosphere could indeed bring about an ice age — and that doubling CO 2 would raise global temperatures by around 5 to 6 degrees C.

It was a remarkably prescient finding for work that, out of necessity, had simplified Earth’s complex climate system down to just a few variables. But Arrhenius’ findings didn’t gain much traction with other scientists at the time. The climate system seemed too large, complex and inert to change in any meaningful way on a timescale that would be relevant to human society. Geologic evidence showed, for instance, that ice ages took thousands of years to start and end. What was there to worry about?

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One researcher, though, thought the idea was worth pursuing. Guy Stewart Callendar, a British engineer and amateur meteorologist, had tallied weather records over time, obsessively enough to determine that average temperatures were increasing at 147 weather stations around the globe. In a 1938 paper in a Royal Meteorological Society journal, he linked this temperature rise to the burning of fossil fuels . Callendar estimated that fossil fuel burning had put around 150 billion metric tons of CO 2 into the atmosphere since the late 19th century.

Like many of his day, Callendar didn’t see global warming as a problem. Extra CO 2 would surely stimulate plants to grow and allow crops to be farmed in new regions. “In any case the return of the deadly glaciers should be delayed indefinitely,” he wrote. But his work revived discussions tracing back to Tyndall and Arrhenius about how the planetary system responds to changing levels of gases in the atmosphere. And it began steering the conversation toward how human activities might drive those changes.

When World War II broke out the following year, the global conflict redrew the landscape for scientific research. Hugely important wartime technologies, such as radar and the atomic bomb, set the stage for “big science” studies that brought nations together to tackle high-stakes questions of global reach. And that allowed modern climate science to emerge.

The Keeling curve

One major effort was the International Geophysical Year, or IGY, an 18-month push in 1957–1958 that involved a wide array of scientific field campaigns including exploration in the Arctic and Antarctica. Climate change wasn’t a high research priority during the IGY, but some scientists in California, led by Roger Revelle of the Scripps Institution of Oceanography, used the funding influx to begin a project they’d long wanted to do. The goal was to measure CO 2 levels at different locations around the world, accurately and consistently.

The job fell to geochemist Charles David Keeling, who put ultraprecise CO 2 monitors in Antarctica and on the Hawaiian volcano of Mauna Loa. Funds soon ran out to maintain the Antarctic record, but the Mauna Loa measurements continued. Thus was born one of the most iconic datasets in all of science — the “Keeling curve,” which tracks the rise of atmospheric CO 2 .

When Keeling began his measurements in 1958, CO 2 made up 315 parts per million of the global atmosphere. Within just a few years it became clear that the number was increasing year by year. Because plants take up CO 2 as they grow in spring and summer and release it as they decompose in fall and winter, CO 2 concentrations rose and fell each year in a sawtooth pattern. But superimposed on that pattern was a steady march upward.

“The graph got flashed all over the place — it was just such a striking image,” says Ralph Keeling, who is Keeling’s son. Over the years, as the curve marched higher, “it had a really important role historically in waking people up to the problem of climate change.” The Keeling curve has been featured in countless earth science textbooks, congressional hearings and in Al Gore’s 2006 documentary on climate change, An Inconvenient Truth .

Each year the curve keeps going up: In 2016, it passed 400 ppm of CO 2 in the atmosphere as measured during its typical annual minimum in September. Today it is at 413 ppm. (Before the Industrial Revolution, CO 2 levels in the atmosphere had been stable for centuries at around 280 ppm.)

Around the time that Keeling’s measurements were kicking off, Revelle also helped develop an important argument that the CO 2 from human activities was building up in Earth’s atmosphere. In 1957, he and Hans Suess, also at Scripps at the time, published a paper that traced the flow of radioactive carbon through the oceans and the atmosphere . They showed that the oceans were not capable of taking up as much CO 2 as previously thought; the implication was that much of the gas must be going into the atmosphere instead.

Steady rise 

Known as the Keeling curve, this chart shows the rise in CO 2 levels as measured at the Mauna Loa Observatory in Hawaii due to human activities. The visible sawtooth pattern is due to seasonal plant growth: Plants take up CO 2   in the growing seasons, then release it as they decompose in fall and winter.

Monthly average CO 2 concentrations at Mauna Loa Observatory

“Human beings are now carrying out a large-scale geophysical experiment of a kind that could not have happened in the past nor be reproduced in the future,” Revelle and Suess wrote in the paper. It’s one of the most famous sentences in earth science history.

Here was the insight underlying modern climate science: Atmospheric carbon dioxide is increasing, and humans are causing the buildup. Revelle and Suess became the final piece in a puzzle dating back to Svante Arrhenius and John Tyndall. “I tell my students that to understand the basics of climate change, you need to have the cutting-edge science of the 1860s, the cutting-edge math of the 1890s and the cutting-edge chemistry of the 1950s,” says Joshua Howe, an environmental historian at Reed College in Portland, Ore.

Evidence piles up

Observational data collected throughout the second half of the 20th century helped researchers gradually build their understanding of how human activities were transforming the planet.

Ice cores pulled from ice sheets, such as that atop Greenland, offer some of the most telling insights for understanding past climate change. Each year, snow falls atop the ice and compresses into a fresh layer of ice representing climate conditions at the time it formed. The abundance of certain forms, or isotopes, of oxygen and hydrogen in the ice allows scientists to calculate the temperature at which it formed, and air bubbles trapped within the ice reveal how much carbon dioxide and other greenhouse gases were in the atmosphere at that time. So drilling down into an ice sheet is like reading the pages of a history book that go back in time the deeper you go.

Scientists began reading these pages in the early 1960s, using ice cores drilled at a U.S. military base in northwest Greenland . Contrary to expectations that past climates were stable, the cores hinted that abrupt climate shifts had happened over the last 100,000 years. By 1979, an international group of researchers was pulling another deep ice core from a second location in Greenland — and it, too, showed that abrupt climate change had occurred in the past. In the late 1980s and early 1990s, a pair of European- and U.S.-led drilling projects retrieved even deeper cores from near the top of the ice sheet, pushing the record of past temperatures back a quarter of a million years.

Together with other sources of information, such as sediment cores drilled from the seafloor and molecules preserved in ancient rocks, the ice cores allowed scientists to reconstruct past temperature changes in extraordinary detail. Many of those changes happened alarmingly fast. For instance, the climate in Greenland warmed abruptly more than 20 times in the last 80,000 years , with the changes occurring in a matter of decades. More recently, a cold spell that set in around 13,000 years ago suddenly came to an end around 11,500 years ago — and temperatures in Greenland rose 10 degrees C in a decade.

Evidence for such dramatic climate shifts laid to rest any lingering ideas that global climate change would be slow and unlikely to occur on a timescale that humans should worry about. “It’s an important reminder of how ‘tippy’ things can be,” says Jessica Tierney, a paleoclimatologist at the University of Arizona in Tucson.

More evidence of global change came from Earth-observing satellites, which brought a new planet-wide perspective on global warming beginning in the 1960s. From their viewpoint in the sky, satellites have measured the rise in global sea level — currently 3.4 millimeters per year and accelerating, as warming water expands and as ice sheets melt — as well as the rapid decline in ice left floating on the Arctic Ocean each summer at the end of the melt season. Gravity-sensing satellites have “weighed” the Antarctic and Greenlandic ice sheets from above since 2002, reporting that more than 400 billion metric tons of ice are lost each year.

Temperature observations taken at weather stations around the world also confirm that we are living in the hottest years on record. The 10 warmest years since record keeping began in 1880 have all occurred since 2005 . And nine of those 10 have come since 2010.

Worrisome predictions

By the 1960s, there was no denying that the planet was warming. But understanding the consequences of those changes — including the threat to human health and well-being — would require more than observational data. Looking to the future depended on computer simulations: complex calculations of how energy flows through the planetary system.

A first step in building such climate models was to connect everyday observations of weather to the concept of forecasting future climate. During World War I, British mathematician Lewis Fry Richardson imagined tens of thousands of meteorologists, each calculating conditions for a small part of the atmosphere but collectively piecing together a global forecast.

But it wasn’t until after World War II that computational power turned Richardson’s dream into reality. In the wake of the Allied victory, which relied on accurate weather forecasts for everything from planning D-Day to figuring out when and where to drop the atomic bombs, leading U.S. mathematicians acquired funding from the federal government to improve predictions. In 1950, a team led by Jule Charney, a meteorologist at the Institute for Advanced Study in Princeton, N.J., used the ENIAC, the first U.S. programmable, electronic computer, to produce the first computer-driven regional weather forecast . The forecasting was slow and rudimentary, but it built on Richardson’s ideas of dividing the atmosphere into squares, or cells, and computing the weather for each of those. The work set the stage for decades of climate modeling to follow.

By 1956, Norman Phillips, a member of Charney’s team, had produced the world’s first general circulation model, which captured how energy flows between the oceans, atmosphere and land. The field of climate modeling was born.

The work was basic at first because early computers simply didn’t have much computational power to simulate all aspects of the planetary system.

An important breakthrough came in 1967, when meteorologists Syukuro Manabe and Richard Wetherald — both at the Geophysical Fluid Dynamics Laboratory in Princeton, a lab born from Charney’s group — published a paper in the Journal of the Atmospheric Sciences that modeled connections between Earth’s surface and atmosphere and calculated how changes in CO 2 would affect the planet’s temperature. Manabe and Wetherald were the first to build a computer model that captured the relevant processes that drive climate , and to accurately simulate how the Earth responds to those processes.

The rise of climate modeling allowed scientists to more accurately envision the impacts of global warming. In 1979, Charney and other experts met in Woods Hole, Mass., to try to put together a scientific consensus on what increasing levels of CO 2 would mean for the planet. The resulting “Charney report” concluded that rising CO 2 in the atmosphere would lead to additional and significant climate change.

In the decades since, climate modeling has gotten increasingly sophisticated . And as climate science firmed up, climate change became a political issue.

The hockey stick 

This famous graph, produced by scientist Michael Mann and colleagues, and then reproduced in a 2001 report by the Intergovernmental Panel on Climate Change, dramatically captures temperature change over time. Climate change skeptics made it the center of an all-out attack on climate science.

The rising public awareness of climate change, and battles over what to do about it, emerged alongside awareness of other environmental issues in the 1960s and ’70s. Rachel Carson’s 1962 book Silent Spring , which condemned the pesticide DDT for its ecological impacts, catalyzed environmental activism in the United States and led to the first Earth Day in 1970.

In 1974, scientists discovered another major global environmental threat — the Antarctic ozone hole, which had some important parallels to and differences from the climate change story. Chemists Mario Molina and F. Sherwood Rowland, of the University of California, Irvine, reported that chlorofluorocarbon chemicals, used in products such as spray cans and refrigerants, caused a chain of reactions that gnawed away at the atmosphere’s protective ozone layer . The resulting ozone hole, which forms over Antarctica every spring, allows more ultraviolet radiation from the sun to make it through Earth’s atmosphere and reach the surface, where it can cause skin cancer and eye damage.

Governments worked under the auspices of the United Nations to craft the 1987 Montreal Protocol, which strictly limited the manufacture of chlorofluorocarbons . In the years following, the ozone hole began to heal. But fighting climate change is proving to be far more challenging. Transforming entire energy sectors to reduce or eliminate carbon emissions is much more difficult than replacing a set of industrial chemicals.

In 1980, though, researchers took an important step toward banding together to synthesize the scientific understanding of climate change and bring it to the attention of international policy makers. It started at a small scientific conference in Villach, Austria, on the seriousness of climate change. On the train ride home from the meeting, Swedish meteorologist Bert Bolin talked with other participants about how a broader, deeper and more international analysis was needed. In 1988, a United Nations body called the Intergovernmental Panel on Climate Change, the IPCC, was born. Bolin was its first chairperson.

The IPCC became a highly influential and unique body. It performs no original scientific research; instead, it synthesizes and summarizes the vast literature of climate science for policy makers to consider — primarily through massive reports issued every couple of years. The first IPCC report, in 1990 , predicted that the planet’s global mean temperature would rise more quickly in the following century than at any point in the last 10,000 years, due to increasing greenhouse gases in the atmosphere.

IPCC reports have played a key role in providing scientific information for nations discussing how to stabilize greenhouse gas concentrations. This process started with the Rio Earth Summit in 1992 , which resulted in the U.N. Framework Convention on Climate Change. Annual U.N. meetings to tackle climate change led to the first international commitments to reduce emissions, the Kyoto Protocol of 1997 . Under it, developed countries committed to reduce emissions of CO 2 and other greenhouse gases. By 2007, the IPCC declared the reality of climate warming is “unequivocal.” The group received the Nobel Peace Prize that year, along with Al Gore, for their work on climate change.

The IPCC process ensured that policy makers had the best science at hand when they came to the table to discuss cutting emissions. Of course, nations did not have to abide by that science — and they often didn’t. Throughout the 2000s and 2010s, international climate meetings discussed less hard-core science and more issues of equity. Countries such as China and India pointed out that they needed energy to develop their economies and that nations responsible for the bulk of emissions through history, such as the United States, needed to lead the way in cutting greenhouse gases.

Meanwhile, residents of some of the most vulnerable nations, such as low-lying islands that are threatened by sea level rise, gained visibility and clout at international negotiating forums. “The issues around equity have always been very uniquely challenging in this collective action problem,” says Rachel Cleetus, a climate policy expert with the Union of Concerned Scientists in Cambridge, Mass.

By 2015, the world’s nations had made some progress on the emissions cuts laid out in the Kyoto Protocol, but it was still not enough to achieve substantial global reductions. That year, a key U.N. climate conference in Paris produced an international agreement to try to limit global warming to 2 degrees C, and preferably 1.5 degrees C , above preindustrial levels.

Every country has its own approach to the challenge of addressing climate change. In the United States, which gets approximately 80 percent of its energy from fossil fuels, sophisticated efforts to downplay and critique the science led to major delays in climate action. For decades, U.S. fossil fuel companies such as ExxonMobil worked to influence politicians to take as little action on emissions reductions as possible.

Biggest footprint 

These 20 nations have emitted the largest cumulative amounts of carbon dioxide since 1850. Emissions are shown in billions of metric tons and are broken down into subtotals from fossil fuel use and cement manufacturing (blue) and land use and forestry (green).

Total carbon dioxide emissions by country, 1850–2021 

Such tactics undoubtedly succeeded in feeding politicians’ delay on climate action in the United States, most of it from Republicans. President George W. Bush withdrew the country from the Kyoto Protocol in 2001 ; Donald Trump similarly rejected the Paris accord in 2017 . As late as 2015, the chair of the Senate’s environment committee, James Inhofe of Oklahoma, brought a snowball into Congress on a cold winter’s day to argue that human-caused global warming is a “hoax.”

In Australia, a similar mix of right-wing denialism and fossil fuel interests has kept climate change commitments in flux, as prime ministers are voted in and out over fierce debates about how the nation should act on climate.

Yet other nations have moved forward. Some European countries such as Germany aggressively pursued renewable energies, including wind and solar, while activists such as Swedish teenager Greta Thunberg — the vanguard of a youth-action movement — pressured their governments for more.

In recent years, the developing economies of China and India have taken center stage in discussions about climate action. China, which is now the world’s largest carbon emitter, declared several moderate steps in 2021 to reduce emissions, including that it would stop building coal-burning power plants overseas. India announced it would aim for net-zero emissions by 2070, the first time it has set a date for this goal.

Yet such pledges continue to be criticized. At the 2021 U.N. Climate Change Conference in Glasgow, Scotland, India was globally criticized for not committing to a complete phaseout of coal — although the two top emitters, China and the United States, have not themselves committed to phasing out coal. “There is no equity in this,” says Aayushi Awasthy, an energy economist at the University of East Anglia in England.

Past and future 

Various scenarios for how greenhouse gas emissions might change going forward help scientists predict future climate change. This graph shows the simulated historical temperature trend along with future projections of rising temperatures based on five scenarios from the Intergovernmental Panel on Climate Change. Temperature change is the difference from the 1850–1900 average.

Historical and projected global temperature change

Facing the future

In many cases, changes are coming faster than scientists had envisioned a few decades ago. The oceans are becoming more acidic as they absorb CO 2 , harming tiny marine organisms that build protective calcium carbonate shells and are the base of the marine food web. Warmer waters are bleaching coral reefs. Higher temperatures are driving animal and plant species into areas in which they previously did not live, increasing the risk of extinction for many.

No place on the planet is unaffected. In many areas, higher temperatures have led to major droughts, which dry out vegetation and provide additional fuel for wildfires such as those that have devastated Australia , the Mediterranean and western North America in recent years.

Then there’s the Arctic, where temperatures are rising at more than twice the global average and communities are at the forefront of change. Permafrost is thawing, destabilizing buildings, pipelines and roads. Caribou and reindeer herders worry about the increased risk of parasites for the health of their animals. With less sea ice available to buffer the coast from storm erosion, the Inupiat village of Shishmaref, Alaska, risks crumbling into the sea . It will need to move from its sand-barrier island to the mainland.

“We know these changes are happening and that the Titanic is sinking,” says Louise Farquharson, a geomorphologist at the University of Alaska Fairbanks who monitors permafrost and coastal change around Alaska. All around the planet, those who depend on intact ecosystems for their survival face the greatest threat from climate change. And those with the least resources to adapt to climate change are the ones who feel it first.

“We are going to warm,” says Claudia Tebaldi, a climate scientist at Lawrence Berkeley National Laboratory in California. “There is no question about it. The only thing that we can hope to do is to warm a little more slowly.”

That’s one reason why the IPCC report released in 2021 focuses on anticipated levels of global warming . There is a big difference between the planet warming 1.5 degrees versus 2 degrees or 2.5 degrees. Each fraction of a degree of warming increases the risk of extreme events such as heat waves and heavy rains, leading to greater global devastation.

The future rests on how much nations are willing to commit to cutting emissions and whether they will stick to those commitments. It’s a geopolitical balancing act the likes of which the world has never seen.

Science can and must play a role going forward. Improved climate models will illuminate what changes are expected at the regional scale, helping officials prepare. Governments and industry have crucial parts to play as well. They can invest in technologies, such as carbon sequestration, to help decarbonize the economy and shift society toward more renewable sources of energy.

Huge questions remain. Do voters have the will to demand significant energy transitions from their governments? How can business and military leaders play a bigger role in driving climate action? What should be the role of low-carbon energy sources that come with downsides, such as nuclear energy? How can developing nations achieve a better standard of living for their people while not becoming big greenhouse gas emitters? How can we keep the most vulnerable from being disproportionately harmed during extreme events, and incorporate environmental and social justice into our future?

These questions become more pressing each year, as carbon dioxideaccumulates in our atmosphere. The planet is now at higher levels of CO 2 than at any time in the last 3 million years.

At the U.N. climate meeting in Glasgow in 2021, diplomats from around the world agreed to work more urgently to shift away from using fossil fuels. They did not, however, adopt targets strict enough to keep the world below a warming of 1.5 degrees.

It’s been well over a century since chemist Svante Arrhenius recognized the consequences of putting extra carbon dioxide into the atmosphere. Yet the world has not pulled together to avoid the most dangerous consequences of climate change.

Time is running out.

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Global Warming Is Real: Fundamentals of the Phenomenon Essay

• To find inspiration for your paper and overcome writer’s block
• As a source of information (ensure proper referencing)
• As a template for you assignment

When speaking about global warming, I would like to highlight the fundamentals of the phenomena. So, first of all, there is a need to point out that global warming seems to be not only an environmental and climatic issue, but also one of the most important mechanisms of evolution. In other words, global warming is considered to be the reason of evolution.

Moore states that “The dire forecasts of global warming hinge on a prediction that human activity will provoke a continued upsurge in atmospheric carbon dioxide” (par. 4). Many scientists are sure that it is human activity, which causes the phenomena.

For instance, they say that “the burning of fossil fuels, the release of methane from agricultural activities, the escape of other chemicals into the air over the next few decades will lead to an effective doubling of greenhouse gases sometime in the next century” (Moore, par. 4).

When speaking about the expected effects of global warming, one is to keep in mind that such climatic changes mostly affect agriculture and fishing.

Most of extractive industries, however, do not suffer from destructive climate shifts. Among potentially disastrous effects disappearance of island countries is considered to be one of the most essential consequences of global warming, as sea level rises and polar ice melts.

Generally, global warming seems to be a complicated problem, as some scientists say that the phenomenon is a global public good. Due to certain scientific and economic uncertainties, there is no opportunity to say for sure how to slow or prevent serious climate shifts.

Global warming is related to numerous disciplines. Ecologists are concerned about ecosystems, marine biologists see global warming as “a problem arising from ocean acidification, utilities as a debit to their balance sheets, and coal miners as an existential threat to their livelihood” (Nordhaus 5). Businessmen and politicians consider the problem of global warming as a great opportunity and as a source of financial aid. An opportunity to balance the economic costs and ecological benefits is considered to be one of the key problems.

They say that human activity and social behaviors are the key aspects of global warming. There are numerous perspectives and theories sociologists rely on to investigate the reasons of global climate changes.

From the sociological point of view, the primary goals of the investigation on global warming include identifying key areas of sociological knowledge concerning climate shifts; outlining important gaps in sociological studies on the above-mentioned topic, facilitating interaction among the workers in sociological sphere, motivating sociologists to study the reasons of climate changes, etc.

“The role of multi-national corporations in producing and responding to climate change (sometimes simply by “greenwashing” their products) has been well documented by environmental sociologists” (Nagel, Dietz & Broadbent 15). Taking into account technological innovations and adaptations, it becomes obvious that the era of the so-called informational war has also impacted on climate changes.

It is evident that people’s health depends upon the health of our planet. Generally, one is to understand that health doesn’t mean only the absence of some problems (mental or other ones).

The diseases are often caused by various changes, including those ones, which are related to biodiversity, watersheds or climate changes. So, global warming hurts not only animal and plants, but it also impacts on people’s health. Such phenomenon as global warming affects many parts of the planet.

When plants die, the animals lose their food. Of course, the animals can adapt to some environmental changes, but nobody will deny the fact that they also can die. People lose their sources of food. The described events are mostly associated with a break in a chain reaction. Potentially, the above-mentioned perspectives are possible.

Global climate change is considered to be “a long-term environmental and societal challenge that affects numerous generations of people in every nation around the world. It is subtle in some ways, blatant in others and will exert a powerful and potentially crippling influence on the world” (“Guidelines for K12 Global Climate Change Education,” 2).

So, when speaking about solving the problem of global warming, it is necessary to point out that people are to do their best to save the planet.

For instance, solving global warming will improve our lives by cleaning up air pollution while investing in clean energy, green jobs and smart energy solutions that get the U.S. economy moving again.

We need to drive smarter cars, save money with energy efficient homes and offices, and build better communities and transportation networks (“Global Warming,” par. 2).

On the other hand, it should be pointed out that according to the opinion of some scientists, global warming is considered to be a natural process, and there is no problem at all.

Of course, it is difficult to believe that the destructive process can be a part of a natural cycle; so, a person’s consciousness is one of the most significant issues the ecologists are to remember about to solve a problem.

Works Cited

“ Global Warming .” Natural Resources Defense Council. Web.

“ Guidelines for K12 Global Climate Change Education .” National Wildlife Federation. Web.

Moore, Thomas. Global Warming: A Boon to Humans and Other Animals , 1995. Web.

Nagel, Joane, Dietz, Thomas & Broadbent, Jeffrey. Sociological Perspectives on Global Climate Change , 2008. Web.

Nordhaus, William. The Challenge of Global Warming: Economic Models and Environmental Policy , 2007. Web.

• The Seriousness of Global Warming
• Flattening of the World: Globalization and Outsourcing
• Oil Sands in Canada: Source Summary
• Large-Scale Patterns of Climatic Variations
• Climate Economists’ Input Into Planet Protection
• Environmental Injustice in Modern World
• Sustainability Project: CERES Educational Park
• Concepts of Global Warming: Survival of Living Organisms
• Global Warming Causes and Unfavorable Climatic Changes
• Global Warming - The Biggest Threat in the 21st Century
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• Chicago (N-B)

IvyPanda. (2019, April 1). Global Warming Is Real: Fundamentals of the Phenomenon. https://ivypanda.com/essays/global-warming-is-real/

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April 8, 2009

Is Global Warming a Myth?

How to respond to people who doubt the human impact on the climate

Dear EarthTalk: I keep meeting people who say that human-induced global warming is only theory, that just as many scientists doubt it as believe it. Can you settle the score? -- J. Proctor, London, UK

So-called “global warming skeptics” are indeed getting more vocal than ever, and banding together to show their solidarity against the scientific consensus that has concluded that global warming is caused by emissions from human activities.

Upwards of 800 skeptics (most of whom are not scientists) took part in the second annual International Conference on Climate Change—sponsored by the Heartland Institute, a conservative think tank—in March 2009. Keynote speaker and Massachusetts Institute of Technology meteorologist Richard Lindzen told the gathering that “there is no substantive basis for predictions of sizeable global warming due to observed increases in minor greenhouse gases such as carbon dioxide, methane and chlorofluorocarbons.”

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Most skeptics attribute global warming—few if any doubt any longer that the warming itself is occurring, given the worldwide rise in surface temperature—to natural cycles, not emissions from power plants, automobiles and other human activity. “The observational evidence…suggests that any warming from the growth of greenhouse gases is likely to be minor, difficult to detect above the natural fluctuations of the climate, and therefore inconsequential,” says atmospheric physicist Fred Singer, an outspoken global warming skeptic and founder of the advocacy-oriented Science and Environmental Policy Project.

But green leaders maintain that even if some warming is consistent with millennial cycles, something is triggering the current change. According to the nonprofit Environmental Defense, some possible (natural) explanations include increased output from the sun, increased absorption of the sun’s heat due to a change in the Earth’s reflectivity, or a change in the internal climate system that transfers heat to the atmosphere.

But scientists have not been able to validate any such reasons for the current warming trend, despite exhaustive efforts. And a raft of recent peer reviewed studies—many which take advantage of new satellite data—back up the claim that it is emissions from tailpipes, smokestacks (and now factory farmed food animals, which release methane) that are causing potentially irreparable damage to the environment.

To wit, the U.S. National Academy of Sciences declared in 2005 that “greenhouse gases are accumulating in Earth’s atmosphere as a result of human activities, causing surface air temperatures and subsurface ocean temperatures to rise,” adding that “the scientific understanding of climate change is now sufficiently clear to justify nations taking prompt action.” Other leading U.S. scientific bodies, including the American Meteorological Society, the American Association for the Advancement of Science and the American Geophysical Union have issued concurring statements—placing the blame squarely on humans’ shoulders.

Also, the Intergovernmental Panel on Climate Change (IPCC), a group of 600 leading climate scientists from 40 nations, says it is “very likely” (more than a 90 percent chance) that humans are causing a global temperature change that will reach between 3.2 and 7.2 degrees Fahrenheit by the end of this century.

CONTACTS : Heartland Institute, www.heartland.org ; Science and Environmental Policy Project, www.sepp.org ; U.S. National Academy of Sciences, www.nas.edu; IPCC , www.ipcc.ch.

EarthTalk is produced by E/The Environmental Magazine. SEND YOUR ENVIRONMENTAL QUESTIONS TO: EarthTalk , P.O. Box 5098, Westport, CT 06881; [email protected] . Read past columns at: www.emagazine.com/earthtalk/archives.php . EarthTalk is now a book! Details and order information at: www.emagazine.com/earthtalkbook .

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Is Climate Change Real?

By definition, climate change is the periodic modification of Earth’s climate due to changes in the atmosphere and interactions between the atmosphere and other geologic, chemical, biological, and geographic factors within the Earth system. All living things respond to climate and changes in the climate, even if these changes are subtle and temporary. Some of the most noticeable examples include the shedding of leaves by flowering plants when water availability is low and shelter-seeking behaviors and dormancy in animals in response to colder or drier conditions. It seems that life on Earth is adapted to tolerating a changing climate to some degree, and this is evidence that climate changes, but our own experience of climate throughout our lifetimes, along with scientific records, also proves that climate change is happening.

Every place on Earth experiences seasonal variation in climate (though the shift can be slight in some tropical regions), and this variation is caused by seasonal changes in the amount of sunlight (solar radiation) reaching Earth’s atmosphere and surface. Year-to-year climate changes also occur; they include droughts, floods, and other events caused by a complex array of factors and Earth system interactions—including atmospheric and oceanic circulation patterns (such as El Niño , La Niña , the North Atlantic Oscillation , etc.)—that affect the paths of storm tracks and the movements of air masses. Climate variations also take place at timescales lasting decades, with clusters of wet, dry, cool, or warm conditions that span several years in a row for given locations. At timescales of thousands of years beyond human lifetimes, climate responds to the precession (slow rotation or “wobble”) of Earth’s axis, the planet’s tilt (obliquity), and the changes to the elliptical shape (eccentricity) of Earth’s orbit. These phenomena interact with one another to determine the amount of sunlight (and thus solar heating) different parts of Earth’s surface receive during different seasons of the year. We must also consider that the amount of radiant energy Earth receives from the Sun is slowly increasing, which adds more and more energy to the mix over time.

Is climate change real? The natural phenomena described above demonstrate that it is, but this is not the whole story. Human activities also affect climate, and a consensus of scientists are sure that the impact of these activities is playing an ever-greater role in determining what form Earth’s climate takes.

Some 97 percent of scientists involved in climate research agree that it is extremely likely that much of the warming observed since the early 1900s results from human activities. Several lines of evidence support this. One of the main strands has to do with the concept of radiative forcing —that is, the heating effect provided by different influencing factors (such as the albedo , or reflectivity, of the land and water and the concentrations of certain gases and particulates in the atmosphere). A component of radiative forcing can be positive (in that it contributes to warming) or negative (in that it has the effect of cooling Earth’s surface). If we consider warming from an energy-budget perspective, on average about 342 watts of solar radiation strike each square meter of Earth’s surface per year, and this quantity can in turn be related to a rise or fall in Earth’s surface temperature. The influence of positive forcings (which are mainly dominated by rising concentrations of greenhouse gases [carbon dioxide, methane, nitrous oxides, and other gases that absorb infrared energy released by Earth’s surface after sunset each day]) has outpaced the cooling influence of aerosols (such as sulfur dioxide from volcanic eruptions and industry) and other negative forcings, adding the equivalent of a little more than two watts per square meter since the middle of the 20th century. Other lines of evidence, including decreasing Arctic sea ice coverage and rising global temperature averages (showing that many of the warmest years have occurred since 1980), support the argument that Earth’s global and regional climates are changing rapidly, very likely much faster than they would if Earth’s climate changes were purely driven by natural forces. As a result, an increasing number of scientists wonder if global and regional climates are changing too quickly for many forms of life to adapt and survive.

ENCYCLOPEDIC ENTRY

Global warming.

The causes, effects, and complexities of global warming are important to understand so that we can fight for the health of our planet.

Earth Science, Climatology

Tennessee Power Plant

Ash spews from a coal-fueled power plant in New Johnsonville, Tennessee, United States.

Photograph by Emory Kristof/ National Geographic

Global warming is the long-term warming of the planet’s overall temperature. Though this warming trend has been going on for a long time, its pace has significantly increased in the last hundred years due to the burning of fossil fuels . As the human population has increased, so has the volume of fossil fuels burned. Fossil fuels include coal, oil, and natural gas, and burning them causes what is known as the “greenhouse effect” in Earth’s atmosphere.

The greenhouse effect is when the sun’s rays penetrate the atmosphere, but when that heat is reflected off the surface cannot escape back into space. Gases produced by the burning of fossil fuels prevent the heat from leaving the atmosphere. These greenhouse gasses are carbon dioxide , chlorofluorocarbons, water vapor , methane , and nitrous oxide . The excess heat in the atmosphere has caused the average global temperature to rise overtime, otherwise known as global warming.

Global warming has presented another issue called climate change. Sometimes these phrases are used interchangeably, however, they are different. Climate change refers to changes in weather patterns and growing seasons around the world. It also refers to sea level rise caused by the expansion of warmer seas and melting ice sheets and glaciers . Global warming causes climate change, which poses a serious threat to life on Earth in the forms of widespread flooding and extreme weather. Scientists continue to study global warming and its impact on Earth.

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There is unequivocal evidence that Earth is warming at an unprecedented rate. Human activity is the principal cause.

• While Earth’s climate has changed throughout its history , the current warming is happening at a rate not seen in the past 10,000 years.
• According to the Intergovernmental Panel on Climate Change ( IPCC ), "Since systematic scientific assessments began in the 1970s, the influence of human activity on the warming of the climate system has evolved from theory to established fact." 1
• Scientific information taken from natural sources (such as ice cores, rocks, and tree rings) and from modern equipment (like satellites and instruments) all show the signs of a changing climate.
• From global temperature rise to melting ice sheets, the evidence of a warming planet abounds.

The rate of change since the mid-20th century is unprecedented over millennia.

Earth's climate has changed throughout history. Just in the last 800,000 years, there have been eight cycles of ice ages and warmer periods, with the end of the last ice age about 11,700 years ago marking the beginning of the modern climate era — and of human civilization. Most of these climate changes are attributed to very small variations in Earth’s orbit that change the amount of solar energy our planet receives.

The current warming trend is different because it is clearly the result of human activities since the mid-1800s, and is proceeding at a rate not seen over many recent millennia. 1 It is undeniable that human activities have produced the atmospheric gases that have trapped more of the Sun’s energy in the Earth system. This extra energy has warmed the atmosphere, ocean, and land, and widespread and rapid changes in the atmosphere, ocean, cryosphere, and biosphere have occurred.

Earth-orbiting satellites and new technologies have helped scientists see the big picture, collecting many different types of information about our planet and its climate all over the world. These data, collected over many years, reveal the signs and patterns of a changing climate.

Scientists demonstrated the heat-trapping nature of carbon dioxide and other gases in the mid-19th century. 2 Many of the science instruments NASA uses to study our climate focus on how these gases affect the movement of infrared radiation through the atmosphere. From the measured impacts of increases in these gases, there is no question that increased greenhouse gas levels warm Earth in response.

Scientific evidence for warming of the climate system is unequivocal.

Intergovernmental Panel on Climate Change

Ice cores drawn from Greenland, Antarctica, and tropical mountain glaciers show that Earth’s climate responds to changes in greenhouse gas levels. Ancient evidence can also be found in tree rings, ocean sediments, coral reefs, and layers of sedimentary rocks. This ancient, or paleoclimate, evidence reveals that current warming is occurring roughly 10 times faster than the average rate of warming after an ice age. Carbon dioxide from human activities is increasing about 250 times faster than it did from natural sources after the last Ice Age. 3

The Evidence for Rapid Climate Change Is Compelling:

Global Temperature Is Rising

The planet's average surface temperature has risen about 2 degrees Fahrenheit (1 degrees Celsius) since the late 19th century, a change driven largely by increased carbon dioxide emissions into the atmosphere and other human activities. 4 Most of the warming occurred in the past 40 years, with the seven most recent years being the warmest. The years 2016 and 2020 are tied for the warmest year on record. 5 Image credit: Ashwin Kumar, Creative Commons Attribution-Share Alike 2.0 Generic.

The Ocean Is Getting Warmer

The ocean has absorbed much of this increased heat, with the top 100 meters (about 328 feet) of ocean showing warming of 0.67 degrees Fahrenheit (0.33 degrees Celsius) since 1969. 6 Earth stores 90% of the extra energy in the ocean. Image credit: Kelsey Roberts/USGS

The Ice Sheets Are Shrinking

The Greenland and Antarctic ice sheets have decreased in mass. Data from NASA's Gravity Recovery and Climate Experiment show Greenland lost an average of 279 billion tons of ice per year between 1993 and 2019, while Antarctica lost about 148 billion tons of ice per year. 7 Image: The Antarctic Peninsula, Credit: NASA

Glaciers Are Retreating

Glaciers are retreating almost everywhere around the world — including in the Alps, Himalayas, Andes, Rockies, Alaska, and Africa. 8 Image: Miles Glacier, Alaska Image credit: NASA

Snow Cover Is Decreasing

Satellite observations reveal that the amount of spring snow cover in the Northern Hemisphere has decreased over the past five decades and the snow is melting earlier. 9 Image credit: NASA/JPL-Caltech

Sea Level Is Rising

Global sea level rose about 8 inches (20 centimeters) in the last century. The rate in the last two decades, however, is nearly double that of the last century and accelerating slightly every year. 10 Image credit: U.S. Army Corps of Engineers Norfolk District

Arctic Sea Ice Is Declining

Both the extent and thickness of Arctic sea ice has declined rapidly over the last several decades. 11 Credit: NASA's Scientific Visualization Studio

Extreme Events Are Increasing in Frequency

The number of record high temperature events in the United States has been increasing, while the number of record low temperature events has been decreasing, since 1950. The U.S. has also witnessed increasing numbers of intense rainfall events. 12 Image credit: Régine Fabri,  CC BY-SA 4.0 , via Wikimedia Commons

Ocean Acidification Is Increasing

Since the beginning of the Industrial Revolution, the acidity of surface ocean waters has increased by about 30%. 13 , 14 This increase is due to humans emitting more carbon dioxide into the atmosphere and hence more being absorbed into the ocean. The ocean has absorbed between 20% and 30% of total anthropogenic carbon dioxide emissions in recent decades (7.2 to 10.8 billion metric tons per year). 1 5 , 16 Image credit: NOAA

1. IPCC Sixth Assessment Report, WGI, Technical Summary . B.D. Santer et.al., “A search for human influences on the thermal structure of the atmosphere.” Nature 382 (04 July 1996): 39-46. https://doi.org/10.1038/382039a0. Gabriele C. Hegerl et al., “Detecting Greenhouse-Gas-Induced Climate Change with an Optimal Fingerprint Method.” Journal of Climate 9 (October 1996): 2281-2306. https://doi.org/10.1175/1520-0442(1996)009<2281:DGGICC>2.0.CO;2. V. Ramaswamy, et al., “Anthropogenic and Natural Influences in the Evolution of Lower Stratospheric Cooling.” Science 311 (24 February 2006): 1138-1141. https://doi.org/10.1126/science.1122587. B.D. Santer et al., “Contributions of Anthropogenic and Natural Forcing to Recent Tropopause Height Changes.” Science 301 (25 July 2003): 479-483. https://doi.org/10.1126/science.1084123. T. Westerhold et al., "An astronomically dated record of Earth’s climate and its predictability over the last 66 million years." Science 369 (11 Sept. 2020): 1383-1387. https://doi.org/10.1126/science.1094123

2. In 1824, Joseph Fourier calculated that an Earth-sized planet, at our distance from the Sun, ought to be much colder. He suggested something in the atmosphere must be acting like an insulating blanket. In 1856, Eunice Foote discovered that blanket, showing that carbon dioxide and water vapor in Earth's atmosphere trap escaping infrared (heat) radiation. In the 1860s, physicist John Tyndall recognized Earth's natural greenhouse effect and suggested that slight changes in the atmospheric composition could bring about climatic variations. In 1896, a seminal paper by Swedish scientist Svante Arrhenius first predicted that changes in atmospheric carbon dioxide levels could substantially alter the surface temperature through the greenhouse effect. In 1938, Guy Callendar connected carbon dioxide increases in Earth’s atmosphere to global warming. In 1941, Milutin Milankovic linked ice ages to Earth’s orbital characteristics. Gilbert Plass formulated the Carbon Dioxide Theory of Climate Change in 1956.

3. IPCC Sixth Assessment Report, WG1, Chapter 2 Vostok ice core data; NOAA Mauna Loa CO2 record O. Gaffney, W. Steffen, "The Anthropocene Equation." The Anthropocene Review 4, issue 1 (April 2017): 53-61. https://doi.org/abs/10.1177/2053019616688022.

4. https://www.ncei.noaa.gov/monitoring https://crudata.uea.ac.uk/cru/data/temperature/ http://data.giss.nasa.gov/gistemp

5. https://www.giss.nasa.gov/research/news/20170118/

6. S. Levitus, J. Antonov, T. Boyer, O Baranova, H. Garcia, R. Locarnini, A. Mishonov, J. Reagan, D. Seidov, E. Yarosh, M. Zweng, " NCEI ocean heat content, temperature anomalies, salinity anomalies, thermosteric sea level anomalies, halosteric sea level anomalies, and total steric sea level anomalies from 1955 to present calculated from in situ oceanographic subsurface profile data (NCEI Accession 0164586), Version 4.4. (2017) NOAA National Centers for Environmental Information. https://www.nodc.noaa.gov/OC5/3M_HEAT_CONTENT/index3.html K. von Schuckmann, L. Cheng, L,. D. Palmer, J. Hansen, C. Tassone, V. Aich, S. Adusumilli, H. Beltrami, H., T. Boyer, F. Cuesta-Valero, D. Desbruyeres, C. Domingues, A. Garcia-Garcia, P. Gentine, J. Gilson, M. Gorfer, L. Haimberger, M. Ishii, M., G. Johnson, R. Killick, B. King, G. Kirchengast, N. Kolodziejczyk, J. Lyman, B. Marzeion, M. Mayer, M. Monier, D. Monselesan, S. Purkey, D. Roemmich, A. Schweiger, S. Seneviratne, A. Shepherd, D. Slater, A. Steiner, F. Straneo, M.L. Timmermans, S. Wijffels. "Heat stored in the Earth system: where does the energy go?" Earth System Science Data 12, Issue 3 (07 September 2020): 2013-2041. https://doi.org/10.5194/essd-12-2013-2020.

7. I. Velicogna, Yara Mohajerani, A. Geruo, F. Landerer, J. Mouginot, B. Noel, E. Rignot, T. Sutterly, M. van den Broeke, M. Wessem, D. Wiese, "Continuity of Ice Sheet Mass Loss in Greenland and Antarctica From the GRACE and GRACE Follow-On Missions." Geophysical Research Letters 47, Issue 8 (28 April 2020): e2020GL087291. https://doi.org/10.1029/2020GL087291.

8. National Snow and Ice Data Center World Glacier Monitoring Service

9. National Snow and Ice Data Center D.A. Robinson, D. K. Hall, and T. L. Mote, "MEaSUREs Northern Hemisphere Terrestrial Snow Cover Extent Daily 25km EASE-Grid 2.0, Version 1 (2017). Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: https://doi.org/10.5067/MEASURES/CRYOSPHERE/nsidc-0530.001 . http://nsidc.org/cryosphere/sotc/snow_extent.html Rutgers University Global Snow Lab. Data History

10. R.S. Nerem, B.D. Beckley, J. T. Fasullo, B.D. Hamlington, D. Masters, and G.T. Mitchum, "Climate-change–driven accelerated sea-level rise detected in the altimeter era." PNAS 15, no. 9 (12 Feb. 2018): 2022-2025. https://doi.org/10.1073/pnas.1717312115.

11. https://nsidc.org/cryosphere/sotc/sea_ice.html Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS, Zhang and Rothrock, 2003) http://psc.apl.washington.edu/research/projects/arctic-sea-ice-volume-anomaly/ http://psc.apl.uw.edu/research/projects/projections-of-an-ice-diminished-arctic-ocean/

12. USGCRP, 2017: Climate Science Special Report: Fourth National Climate Assessment, Volume I [Wuebbles, D.J., D.W. Fahey, K.A. Hibbard, D.J. Dokken, B.C. Stewart, and T.K. Maycock (eds.)]. U.S. Global Change Research Program, Washington, DC, USA, 470 pp, https://doi.org/10.7930/j0j964j6 .

13. http://www.pmel.noaa.gov/co2/story/What+is+Ocean+Acidification%3F

14. http://www.pmel.noaa.gov/co2/story/Ocean+Acidification

15. C.L. Sabine, et al., “The Oceanic Sink for Anthropogenic CO2.” Science 305 (16 July 2004): 367-371. https://doi.org/10.1126/science.1097403.

16. Special Report on the Ocean and Cryosphere in a Changing Climate , Technical Summary, Chapter TS.5, Changing Ocean, Marine Ecosystems, and Dependent Communities, Section 5.2.2.3. https://www.ipcc.ch/srocc/chapter/technical-summary/

Header image shows clouds imitating mountains as the sun sets after midnight as seen from Denali's backcountry Unit 13 on June 14, 2019. Credit: NPS/Emily Mesner Image credit in list of evidence: Ashwin Kumar, Creative Commons Attribution-Share Alike 2.0 Generic.

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Climate explained: why some people still think climate change isn’t real

Senior Researcher in Politics, Auckland University of Technology

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Why do people still think climate change isn’t real?

At its heart, climate change denial is a conflict between facts and values. People deny the climate crisis because, to them, it just feels wrong.

As I’ve argued elsewhere , acknowledging climate change involves accepting certain facts. But being concerned about climate change involves connecting these facts to values. It involves building bridges between the science of climate change and peoples’ various causes, commitments and convictions.

Denial happens when climate science rubs us up the wrong way. Instead of making us want to arrest the climate crisis, it makes us resist the very thought of it, because the facts of anthropogenic global heating clash with our personal projects.

It could be that the idea of climate change is a threat to our worldview . Or it could be that we fear society’s response to climate change, the disruption created by the transition to a low-emissions economy . Either way, climate change becomes such an “ inconvenient truth ” that, instead of living with and acting upon our worries, we suppress the truth instead.

Read more: Five climate change science misconceptions – debunked

Negating reality

Sigmund Freud and his daughter Anna were the great chroniclers of denial. Sigmund described this negation of reality as an active mental process, as “a way of taking cognisance of what is repressed”. This fleeting comprehension is what distinguishes denial from ignorance, misunderstanding or sheer disbelief. Climate change denial involves glimpsing the horrible reality, but defending oneself against it.

Contemporary social psychologists tend to talk about this in terms of “ motivated reasoning ”. Because the facts of climate science are in conflict with people’s existing beliefs and values, they reason around the facts.

When this happens – as social psychologist Jonathan Haidt memorably put it – they aren’t reasoning in the careful manner of a judge who impartially weighs up all the evidence. Instead, they’re reasoning in the manner of a defence lawyer who clutches for post hoc rationalisations to defend an initial gut instinct. This is why brow-beating deniers with further climate science is unlikely to succeed: their faculty of reason is motivated to defend itself from revising its beliefs.

A large and growing empirical literature is exploring what drives denial. Personality is a factor: people are more likely to deny climate change if they’re inclined toward hierarchy and against changes to the status quo . Demographic factors also show an effect. Internationally , people who are less educated, older and more religious tend to discount climate change, with sex and income having a smaller effect.

Read more: Climate explained: Why are climate change skeptics often right-wing conservatives?

But the strongest predictor is one’s politics. An international synthesis of existing studies found that values, ideologies and political allegiances overshadowed other factors. In Western societies, political affiliation is the key factor, with conservative voters more likely to discount climate change. Globally, a person’s commitment to democratic values – or not in the case of deniers – is more significant.

This sheds light on another side of the story. Psychology can contribute to explaining a person’s politics, but politics cannot be entirely explained by psychology. So too for denial.

The politics of denial

As the sociologist Stanley Cohen noted in his classic study of denial, there is an important distinction between denial that is personal and psychological, and denial that is institutional and organised. The former involves people who deny the facts to themselves, but the latter involves the denial of facts to others, even when these “ merchants of doubt ” know the truth very well.

It is well established that fossil fuel companies have long known about climate change, yet sought to frustrate wider public understanding. A comprehensive analysis of documentations from ExxonMobil found that, since 1977, the company has internally acknowledged climate change through the publications of its scientists, even while it publicly promoted doubt through paid advertorials. The fossil fuel industry has also invested heavily in conservative foundations and think tanks that promote contrarian scientists and improbable spins on the science.

All this is rich manure for personal denial. When a person’s motivated reasoning is on the hunt for excuses, there is an industry ready to supply them. Social media offers further opportunities for spreading disinformation . For example, a recent analysis of anonymised YouTube searches found that videos supporting the scientific consensus on climate change were outnumbered by those that didn’t.

Undoing denial

In sum, denial is repressed knowledge. For climate change, this repression occurs at both the psychological level and social level, with the latter providing fodder for the former. This is a dismal scenario , but it shines some light on the way forward.

On the one hand, it reminds us that deniers are capable of acknowledging the science – at some level, they already do – even though they struggle to embrace the practical and ethical implications. Consequently, climate communications may do well to appeal to more diverse values, particularly those values held by the deniers themselves.

Experiments have shown that, if the risks and realities of climate change are reframed as opportunities for community relationship building and societal development, then deniers can shift their views. Similarly, in the US context, appealing to conservative values like patriotism, obeying authority and defending the purity of nature can encourage conservatives to support pro-environmental actions.

On the other hand, not all deniers will be convinced. Some downplay and discount climate change precisely because they recognise that the low-emissions transition will adversely impact their interests. A bombardment of further facts and framings is unlikely to move them.

What will make a difference is the power of the people – through regulation, divestment, consumer choice and public protest. Public surveys emphasise that, throughout the world, deniers are in the minority . The worried majority doesn’t need to win over everyone in order to win on climate change.

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Debunking eight common myths about climate change

The world is warming at a  record pace , with unseasonable heat baking nearly every continent on Earth. April, the last month for which statistics are available, marked the 11th consecutive month the planet has set a new temperature high.

Experts say that is a clear sign the Earth’s climate is rapidly changing. But many believe – or at least say they believe – that  climate change  is not real, relying on a series of well-trodden myths to make their point. 

“Most of the world rightly acknowledges that climate change is real,” says Dechen Tsering, Acting Director of the Climate Change Division at the United Nations Environment Programme (UNEP). “But in many places, misinformation is delaying the action that is so vital to countering what is one of the greatest challenges facing humanity.” 

This month, delegates will be meeting in Bonn, Germany for a key conference on climate change. Ahead of that gathering, here is a closer look at eight common climate-related myths and why they are simply not true. 

Myth #1: Climate change has always happened, so we should not worry about it. 

It is true that the planet’s temperature has long fluctuated, with periods of warming and cooling. But since the last ice age 10,000 years ago, the climate has been relatively stable, which scientists say has been crucial to the development of human civilization. 

That stability is now faltering. The Earth is heating up at its fastest rate in at least 2,000 years and is about 1.2°C hotter than it was in pre-industrial times. The last 10 years have been the warmest on record, with 2023 smashing global temperature records.   

Other key climate-related indicators are also spiking. Ocean temperatures , sea levels and  atmospheric concentrations of greenhouse gasses are rising at record rates while sea ice and glaciers are retreating at alarming speeds. 

Myth #2: Climate change is a natural process. It has nothing to do with people. 

While climate change is a natural process human activity is pushing it into overdrive. A landmark report from the Intergovernmental Panel on Climate Change (IPCC), which draws on the research of hundreds of leading climate scientists, found that humans are responsible for almost all the global warming over the past 200 years.  

The vast majority of warming has come from the burning of coal, oil and gas. The combustion of these fossil fuels is flooding the atmosphere with greenhouse gases, which act like a blanket around the planet, trapping heat.  

By measuring everything from ice cores to tree rings, scientists have been able to track concentrations of greenhouse gases. Carbon dioxide levels are at their highest in 2 million years , while two other greenhouse gases, methane and nitrous oxide, are at their highest in 800,000 years .  

Myth #3: A couple of degrees of warming is not that big of a deal. 

Actually, small temperature rises can throw the world’s delicate ecosystems into disarray, with dire implications for humans and other living things. The Paris Agreement on climate change aims to limit average global temperature rise to “well below” 2°C, and preferably to 1.5°C, since pre-industrial times.  

Even that half-a-degree swing could make a massive difference. The IPCC found that at 2°C of warming, more than 2 billion people would regularly be exposed to extreme heat than they would at 1.5°C. The world would also lose twice as many plants and vertebrate species and three times as many insects. In some areas, crop yields would decrease by more than half, threatening food security. 

At 1.5°C of warming, 70 per cent to 90 per cent of corals, the pillars of many undersea ecosystems, would die. At 2°C of warming, some 99 per cent would perish. Their disappearance would likely lead to the loss of other marine species, many of which are a critical source of protein for coastal communities. 

“Every fraction of a degree of warming matters,” says Tsering. 

Myth #4: An increase in cold snaps shows climate change is not real. 

This statement confuses weather and climate, which are two different things. Weather is the day-to-day atmospheric conditions in a location and climate is the long-term weather conditions in a region. So, there could still be a cold snap while the general trend for the planet is warming.  

Some experts also believe climate change could lead to longer and more intense cold in some places due to changes in wind patterns and other atmospheric factors. One much-publicized paper found the rapid warming of the Arctic may have disrupted the swirling mass of cold air above the North Pole in 2021. This unleashed sub-zero temperatures as far south as Texas in the United States, causing billions of dollars in damages. 

Myth #5: Scientists disagree on the cause of climate change. 

A 2021 study revealed that 99 per cent of peer-reviewed scientific literature found that climate change was human-induced. That was in line with a widely read study from 2013 , which found 97 per cent of peer-reviewed papers that examined the causes of climate change said it was human-caused. 

“The idea that there is no consensus is used by climate deniers to muddy the waters and sow the seeds of doubt,” says Tsering. “But the scientific community agrees: the global warming we are facing is not natural. It is caused by humans.” 

Myth #6: It is too late to avert a climate catastrophe, so we might as well keep burning fossil fuels. 

While the situation is dire, there is still a narrow window for humanity to avoid the worst of climate change.  

UNEP’s latest Emissions Gap Report found that cutting greenhouse gas emissions by 42 per cent by 2030, the world could limit global temperature rise to 1.5°C compared with pre-industrial levels.  

A little math reveals that to reach that target, the world must reduce its annual emissions by 22 billion tonnes of carbon-dioxide equivalent in less than seven years. That might seem like a lot. But by ramping up financing and focusing on low-carbon development in key transport , agriculture and forestry, the world can get there.  

“There is no question the task ahead of us is massive,” Tsering says. “But we have the solutions we need to reduce emissions today and there is an opportunity to raise ambition in the new round of national climate action plans.”  

Myth #7: Climate models are unreliable. 

Climate skeptics have long argued that the computer models used to project climate change are unreliable at best and completely inaccurate at worst. 

But the IPCC, the world’s leading scientific authority on climate change, says that over decades of development, these models have consistently provided “a robust and unambiguous picture” of planetary warming.  

Meanwhile, a 2020 study by the University of California showed that global warming models were largely accurate. The study looked at 17 models that were generated between 1970 and 2007 and found 14 of them closely matched observations.  

Myth #8: We do not need to worry about lowering greenhouse gas emissions. Humanity is inventive; we can just adapt to climate change. 

Some countries and communities can adapt to rising temperatures, lower precipitation and the other impacts of climate change. But many cannot.  

The world’s developing countries collectively need between US$215 billion and US$387 billion per year to adapt to climate change, yet only have access to a fraction of that total, found UNEP’s latest Adaptation Gap Report . Even wealthy nations will struggle to afford the cost of adaptation, which in some cases will require radical measures, such as displacing vulnerable communities, relocating vital infrastructure or changing staple foods.  

In many places, people are already facing hard limits on how much they can adapt. Small island developing states , for example, can only do so much to hold back the rising seas that threaten their existence. 

Without significant action to lower greenhouse gas emissions, communities will reach these hard limits faster and begin to suffer irreparable damage from climate change, say experts.   

The Sectoral Solution to the climate crisis  

UNEP is at the forefront of supporting the Paris Agreement goal of keeping global temperature rise well below 2°C, and aiming for 1.5°C, compared to pre-industrial levels. To do this, UNEP has developed the Sectoral Solution, a roadmap to reducing emissions across sectors in line with the Paris Agreement commitments and in pursuit of climate stability. The six sectors identified are: energy; industry; agriculture and food; forests and land use; transport; and buildings and cities. 

Further Resources

• UNEP’s work on climate change
• The Sectoral Solution to Climate Change
• Adaptation Gap Report 2023
• Emissions Gap Report 2023

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The global warming that’s causing our climate crisis is already having dire consequences.

In just the past few decades:

• Rising temperatures have worsened extreme weather events .
• Chunks of ice in the Antarctic have broken apart .
• Wildfire seasons are months longer .
• Coral reefs have been bleached of their colors .
• Mosquitoes are expanding their territory, able to spread disease .

What’s causing this climate crisis?

It’s mainly us.

Humans are the main cause of climate change — we burn fossil fuels and chop down forests, causing average temperatures to rise worldwide. That global warming trend is increasingly disrupting our climate — the average weather over many years.

Earth has already warmed by about 1 degree Celsius, or 1.8 degrees Fahrenheit, since the 19th century, before industry started to boom.

While we experience the effects , we’re on our way toward 1.5 degrees C (2.7 F) by as early as 2030.

7 facts about climate change

Why a half-degree more is such a big deal

A warmer world — even by a half-degree Celsius — has more evaporation, leading to more water in the atmosphere. Such changing conditions put our agriculture, health, water supply and more at risk.

Picture a North Carolina cotton farm that’s been around since 1960, with global average temperatures rising by roughly half a degree since it grew its first crop.

The increased evaporation and additional moisture to the atmosphere has led to 30% more intense rain during heavy downpours in that part of the U.S.

Then a hurricane like 2018’s Florence — already strengthened by warmer oceans and higher seas — dumps this excess rainfall on the farm. The crops get more flooded and damaged than they did half a century ago.

It's how you go from half-degree of warming to economic hardship.

Are record-breaking hurricanes our new normal?

There’s still time to act

Whether it’s a shift of 1.5 degrees or 2 degrees, these warming levels aren’t magic thresholds. Every rise in warming is worse for the planet than the last.

But they're not inevitable.

It's not too late to slow the pace of climate change and avert the worst impacts of the climate crisis — as long as we act today. With your help, we can attack this challenge.

Donate now to have triple the impact in the climate fight

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Analysis: Why scientists think 100% of global warming is due to humans

Zeke Hausfather

The extent of the human contribution to modern global warming is a hotly debated topic in political circles, particularly in the US.

During a recent congressional hearing, Rick Perry, the US energy secretary, remarked that “to stand up and say that 100% of global warming is because of human activity, I think on its face, is just indefensible”.

However, the science on the human contribution to modern warming is quite clear. Humans emissions and activities have caused around 100% of the warming observed since 1950, according to the Intergovernmental Panel on Climate Change’s (IPCC) fifth assessment report .

Here Carbon Brief examines how each of the major factors affecting the Earth’s climate would influence temperatures in isolation – and how their combined effects almost perfectly predict long-term changes in the global temperature.

Carbon Brief’s analysis finds that:

• Since 1850, almost all the long-term warming can be explained by greenhouse gas emissions and other human activities.
• If greenhouse gas emissions alone were warming the planet, we would expect to see about a third more warming than has actually occurred. They are offset by cooling from human-produced atmospheric aerosols.
• Aerosols are projected to decline significantly by 2100 , bringing total warming from all factors closer to warming from greenhouse gases alone.
• Natural variability in the Earth’s climate is unlikely to play a major role in long-term warming.

How much warming is caused by humans?

In its 2013 fifth assessment report, the IPCC stated in its summary for policymakers that it is “extremely likely that more than half of the observed increase in global average surface temperature” from 1951 to 2010 was caused by human activity. By “extremely likely”, it meant that there was between a 95% and 100% probability that more than half of modern warming was due to humans.

This somewhat convoluted statement has been often misinterpreted as implying that the human responsibility for modern warming lies somewhere between 50% and 100%. In fact, as NASA’s Dr Gavin Schmidt has pointed out, the IPCC’s implied best guess was that humans were responsible for around 110% of observed warming (ranging from 72% to 146%), with natural factors in isolation leading to a slight cooling over the past 50 years.

Similarly, the recent US fourth national climate assessment found that between 93% to 123% of observed 1951-2010 warming was due to human activities.

These conclusions have led to some confusion as to how more than 100% of observed warming could be attributable to human activity. A human contribution of greater than 100% is possible because natural climate change associated with volcanoes and solar activity would most likely have resulted in a slight cooling over the past 50 years, offsetting some of the warming associated with human activities.

‘Forcings’ that change the climate

Scientists measure the various factors that affect the amount of energy that reaches and remains in the Earth’s climate. They are known as “radiative forcings”.

These forcings include greenhouse gases, which trap outgoing heat, aerosols – both from human activities and volcanic eruptions – that reflect incoming sunlight and influence cloud formation, changes in solar output, changes in the reflectivity of the Earth’s surface associated with land use, and many other factors.

To assess the role of each different forcing in observed temperature changes, Carbon Brief adapted a simple statistical climate model developed by Dr Karsten Haustein and his colleagues at the University of Oxford and University of Leeds . This model finds the relationship between both human and natural climate forcings and temperature that best matches observed temperatures, both globally and over land areas only.

The figure below shows the estimated role of each different climate forcing in changing global surface temperatures since records began in 1850 – including greenhouse gases (red line), aerosols (dark blue), land use (light blue), ozone (pink), solar (yellow) and volcanoes (orange).

The black dots show observed temperatures from the Berkeley Earth surface temperature project, while the grey line shows the estimated warming from the combination of all the different types of forcings.

The combination of all radiative forcings generally matches longer-term changes in observed temperatures quite well. There is some year-to-year variability, primarily from El Niño events , that is not driven by changes in forcings. There are also periods from 1900-1920 and 1930-1950 where some larger disagreements are evident between projected and observed warming, both in this simple model and in more complex climate models .

The chart highlights that, of all the radiative forcings analysed, only increases in greenhouse gas emissions produce the magnitude of warming experienced over the past 150 years.

If greenhouse gas emissions alone were warming the planet, we would expect to see about a third more warming than has actually occurred.

So, what roles do all the other factors play?

• Q&A: How do climate models work?
• Interactive: The impacts of climate change at 1.5C, 2C and beyond
• Explainer: How scientists estimate ‘climate sensitivity’
• Mapped: How every part of the world has warmed – and could continue to warm

The extra warming from greenhouse gases is being offset by sulphur dioxide and other products of fossil fuel combustion that form atmospheric aerosols . Aerosols in the atmosphere both reflect incoming solar radiation back into space and increase the formation of high, reflective clouds, cooling the Earth.

Ozone is a short-lived greenhouse gas that traps outgoing heat and warms the Earth. Ozone is not emitted directly, but is formed when methane, carbon monoxide, nitrogen oxides and volatile organic compounds break down in the atmosphere. Increases in ozone are directly attributable to human emissions of these gases.

In the upper atmosphere, reductions in ozone associated with chlorofluorocarbons (CFCs) and other halocarbons depleting the ozone layer have had a modest cooling effect. The net effects of combined lower and upper atmospheric ozone changes have modestly warmed the Earth by a few tenths of a degree.

Changes in the way land is used alter the reflectivity of the Earth’s surface. For example, replacing a forest with a field will generally increase the amount of sunlight reflected back into space, particularly in snowy regions. The net climate effect of land-use changes since 1850 is a modest cooling.

Volcanoes have a short-term cooling effect on the climate due to their injection of sulphate aerosols high into the stratosphere, where they can remain aloft for a few years, reflecting incoming sunlight back into space. However, once the sulphates drift back down to the surface, the cooling effect of volcanoes goes away. The orange line shows the estimated impact of volcanoes on the climate, with large downward spikes in temperatures of up to 0.4C associated with major eruptions.

Finally, solar activity is measured by satellites over the past few decades and estimated based on sunspot counts in the more distant past. The amount of energy reaching the Earth from the sun fluctuates modestly on a cycle of around 11 years. There has been a slight increase in overall solar activity since the 1850s, but the amount of additional solar energy reaching the Earth is small compared to other radiative forcings examined.

Over the past 50 years, solar energy reaching the Earth has actually declined slightly , while temperatures have increased dramatically.

Human forcings match observed warming

The accuracy of this model depends on the accuracy of the radiative forcing estimates. Some types of radiative forcing like that from atmospheric CO2 concentrations can be directly measured and have relatively small uncertainties. Others, such as aerosols, are subject to much greater uncertainties due to the difficulty of accurately measuring their effects on cloud formation.

These are accounted for in the figure below, which shows combined natural forcings (blue line) and human forcings (red line) and the uncertainties that the statistical model associates with each. These shaded areas are based on 200 different estimates of radiative forcings, incorporating research attempting to estimate a range of values for each. Uncertainties in human factors increase after 1960, driven largely by increases in aerosol emissions after that point.

Overall, warming associated with all human forcings agrees quite well with observed warming, showing that about 104% of the total since the start of the “modern” period in 1950 comes from human activities (and 103% since 1850), which is similar to the value reported by the IPCC. Combined natural forcings show a modest cooling, primarily driven by volcanic eruptions.

The simple statistical model used for this analysis by Carbon Brief differs from much more complex climate models generally used by scientists to assess the human fingerprint on warming. Climate models do not simply “fit” forcings to observed temperatures. Climate models also include variations in temperature over space and time, and can account for different efficacies of radiative forcings in different regions of the Earth.

However, when analysing the impact of different forcings on global temperatures, complex climate models generally find results similar to simple statistical models. The figure below, from the IPCC’s Fifth Assessment Report, shows the influence of different factors on temperature for the period from 1950 to 2010. Observed temperatures are shown in black, while the sum of human forcings is shown in orange.

This suggests that human forcings alone would have resulted in approximately 110% of observed warming . The IPCC also included the estimated magnitude of internal variability over that period in the models, which they suggest is relatively small and comparable to that of natural forcings.

As Prof Gabi Hegerl at the University of Edinburgh tells Carbon Brief: “The IPCC report has an estimate that basically says the best guess is no contribution [from natural variability] with not that much uncertainty.”

Land areas are warming faster

Land temperatures have warmed considerably faster than average global temperatures over the past century, with temperatures reaching around 1.7C above pre-industrial levels in recent years. The land temperature record also goes back further in time than the global temperature record, though the period prior to 1850 is subject to much greater uncertainties .

Both human and natural radiative forcings can be matched to land temperatures using the statistical model. The magnitude of human and natural forcings will differ a bit between land and global temperatures. For example, volcanic eruptions appear to have a larger influence on land, as land temperatures are likely to respond faster to rapid changes in forcings.

The figure below shows the relative contribution of each different radiative forcing to land temperatures since 1750.

The combination of all forcings generally matches observed temperatures quite well, with short-term variability around the grey line primarily driven by El Niño and La Niña events. There is a wider variation in temperatures prior to 1850, reflecting the much larger uncertainties in the observational records that far back.

There is still a period around 1930 and 1940 where observations exceed what the model predicts, though the differences are less pronounced than in global temperatures and the 1900-1920 divergence is mostly absent in land records.

Volcanic eruptions in the late 1700s and early 1800s stand out sharply in the land record. The eruption of Mount Tambora in Indonesia in 1815 may have cooled land temperatures by a massive 1.5C, though records at the time were limited to parts of the Northern Hemisphere and it is, therefore, hard to draw a firm conclusion about global impacts. In general, volcanoes appear to cool land temperatures by nearly twice as much as global temperatures.

What may happen in the future?

Carbon Brief used the same model to project future temperature changes associated with each forcing factor. The figure below shows observations up to 2017, along with future post-2017 radiative forcings from RCP6.0 , a medium-to-high future warming scenario.

When provided with the radiative forcings for the RCP6.0 scenario, the simple statistical model shows warming of around 3C by 2100, nearly identical to the average warming that climate models find.

Future radiative forcing from CO2 is expected to continue to increase if emissions rise. Aerosols, on the other hand, are projected to peak at today’s levels and decline significantly by 2100 , driven in large part by concerns about air quality. This reduction in aerosols will enhance overall warming, bringing total warming from all radiative forcing closer to warming from greenhouse gases alone. The RCP scenarios assume no specific future volcanic eruptions, as the timing of these is unknowable, while solar output continues its 11-year cycle.

This approach can also be applied to land temperatures, as shown in the figure below. Here, land temperatures are shown between 1750 and 2100, with post-2017 forcings also from RCP6.0.

The land is expected to warm about 30% faster than the globe as a whole, as the rate of warming over the oceans is buffered by ocean heat uptake. This is seen in the model results, where land warms by around 4C by 2100 compared to 3C globally in the RCP6.0 scenario.

There is a wide range of future warming possible from different RCP scenarios and different values for the sensitivity of the climate system , but all show a similar pattern of declining future aerosol emissions and a larger role for greenhouse gas forcing in future temperatures.

The role of natural variability

While natural forcings from solar and volcanoes do not seem to play much of a role in long-term warming, there is also natural variability associated with ocean cycles and variations in ocean heat uptake.

As the vast majority of energy trapped by greenhouse gases is absorbed by the oceans rather than the atmosphere, changes in the rate of ocean heat uptake can potentially have large impacts on the surface temperature. Some researchers have argued that multidecadal cycles, such as the Atlantic Multidecadal Oscillation (AMO) and Pacific Decadal Oscillation (PDO), can play a role in warming at a decadal scale.

While human factors explain all the long-term warming, there are some specific periods that appear to have warmed or cooled faster than can be explained based on our best estimates of radiative forcing. For example, the modest mismatch between the radiative forcing-based estimate and observations during the mid-1900s might be evidence of a role for natural variability during that period.

A number of researchers have examined the potential for natural variability to impact long-term warming trends. They have found that it generally plays a limited role. For example, Dr Markus Huber and Dr Reto Knutti at the Institute for Atmospheric and Climate Science (IAC) in Zurich found a maximum possible contribution of natural variability of around 26% (+/- 12%) over the past 100 years and 18% (+/- 9%) over the past 50 years.

Knutti tells Carbon Brief:

“We can never completely rule out that natural variability is larger than we currently think. But that is a weak argument: you can, of course, never rule out the unknown unknown. The question is whether there is strong, or even any evidence for it. And the answer is no, in my view.

Models get the short-term temperature variability approximately right. In many cases, they even have too much. And for the long term, we can’t be sure because the observations are limited. But the forced response pretty much explains the observations, so there is no evidence from the 20th century that we are missing something…

Even if models were found to underestimate internal variability by a factor of three, it is extremely unlikely [less than 5% chance] that internal variability could produce a trend as large as observed.”

Similarly, Dr Martin Stolpe and colleagues, also at IAC, recently analysed the role of multidecadal natural variability in both the Atlantic and Pacific oceans. They found that “less than 10% of the observed global warming during the second half of the 20th century is caused by internal variability in these two ocean basins, reinforcing the attribution of most of the observed warming to anthropogenic forcings”.

Internal variability is likely to have a much larger role in regional temperatures. For example, in producing unusually warm periods in the Arctic and the US in the 1930s. However, its role in influencing long-term changes in global surface temperatures appears to be limited.

While there are natural factors that affect the Earth’s climate, the combined influence of volcanoes and changes in solar activity would have resulted in cooling rather than warming over the past 50 years.

The global warming witnessed over the past 150 years matches nearly perfectly what is expected from greenhouse gas emissions and other human activity, both in the simple model examined here and in more complex climate models. The best estimate of the human contribution to modern warming is around 100%.

Some uncertainty remains due to the role of natural variability, but researchers suggest that ocean fluctuations and similar factors are unlikely to be the cause of more than a small fraction of modern global warming.

Methodology

The simple statistical model used in this article is adapted from the Global Warming Index published by Haustein et al ( 2017 ). In turn, it is based on the Otto et al ( 2015 ) model.

The model estimates contributions to observed climate change and removes the impact of natural year-to-year fluctuations by a multiple linear regression of observed temperatures and estimated responses to total human-induced and total natural drivers of climate change. The forcing responses are provided by the standard simple climate model given in Chapter 8 of IPCC ( 2013 ), but the size of these responses is estimated by the fit to the observations. The forcings are based on IPCC (2013) values and were updated to 2017 using data from NOAA and ECLIPSE . 200 variations of these forcings were provided by Dr. Piers Forster  of the University of Leeds , reflecting the uncertainty in forcing estimates. An Excel spreadsheet containing their model is also provided.

The model was adapted by calculating forcing responses for each of the different major climate forcings rather than simply total human and natural forcings, using the Berkeley Earth record for observations. The decay time of thermal response used in converting forcings to forcing responses was adjusted to be one year rather than four years for volcanic forcings to better reflect the fast response time present in observations. The effects of El Niño and La Niña (ENSO) events was removed from the observations using an approach adapted from Foster and Rahmstorf ( 2011 ) and the Kaplan El Niño 3.4 index when calculating the volcanic temperature response, as the overlap between volcanoes and ENSO otherwise complicates empirical estimates.

The temperature response for each individual forcing was calculated by scaling their forcing responses by the total human or natural coefficients from the regression model . The regression model was also run separately for land temperatures. Temperature responses for each forcing between 2018 and 2100 were estimated using forcing data from RCP6.0, normalised to match the magnitude of observed forcings at the end of 2017.

Uncertainties in total human and total natural temperature response was estimated using a Monte Carlo analysis of 200 different forcing series, as well as the uncertainties in the estimated regression coefficients. The Python code used to run the model is archived with GitHub and available for download .

Observational data from 2017 shown in the figures is based on the average of the first 10 months of the year and is likely to be quite similar to the ultimate annual value.

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Where My Climate Doubts Began to Melt

By Bret Stephens Oct. 28, 2022

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Yes, Greenland’s Ice Is Melting But...

climate change while reinforcing my belief that markets, not government, provide the cure. --> mind about climate change while reinforcing my belief that markets, not government, provide the cure. --> A trip there changed my mind about climate change while reinforcing my belief that markets, not government, provide the cure. A trip there changed my mind about climate change while reinforcing my belief that markets, not government, provide the cure.

ILULISSAT, Greenland — On a clear day in August, a helicopter set me and a few companions down on the northern end of the Jakobshavn Glacier in Western Greenland, about 150 miles north of the Arctic Circle. The ground under our feet seemed almost lunar: gray silt and dust, loose rocks and boulders, and, at the edge of the glacier’s face, mud so deep it nearly ate my boots. To the south, the calving front of the glacier known in Greenlandic as Sermeq Kujalleq periodically deposited enormous slabs of ice, some more than 100 feet high, into the open water.

I asked the pilot to give me a sense of how much the glacier had retreated since he had been flying the route. He pointed to a distant rocky island in the middle of the fjord.

“That’s where the glacier was in 2007,” he said.

Over the course of the 20th century, the Jakobshavn Glacier retreated about 10 to 15 kilometers. Over just the next eight years, it retreated about the same amount, according to the oceanographer Josh Willis of NASA’s Jet Propulsion Laboratory. Later the front advanced a little — a function of complex dynamics partly involving ocean currents — before resuming its retreat.

For anyone who has entertained doubts about the warming of the planet, a trip to Greenland serves as a bracing corrective. Flying low over the vast ice sheet that covers most of the island, I immediately noticed large ponds of cerulean meltwater and dozens of fast-flowing streams rushing through gullies of white ice and sometimes disappearing into vertical ice caverns thousands of feet deep. Such lakes, scientists report , have become far more common over the last two decades, occurring earlier in the year at higher elevations. Last year, it even rained at the highest point of the ice sheet, some 500 miles north of the Arctic Circle. That’s a first since record keeping began in the 1980s.

Closer to the coast, at the point where the sheet approaches the darkly colored mountains that ring the island, lies a distinctive, beige trimline of barren earth, ranging in width from hundreds to thousands of meters. Like the bathtub rings in the depleted lakes and reservoirs of the American West, it shows where the ice once reached, and how far it has receded. History also records that Greenland’s great 19th-century explorers — men like Fridtjof Nansen of Norway and Robert Peary of America — had to climb steep glacial walls merely to get onto the sheet itself. Now it is easy to spot places where the ice meets the dry land on flat ground.

And then there’s the testimony of the market.

In the coastal town of Ilulissat, I had dinner with Bo Møller Stensgaard, a geologist and the C.E.O. of Bluejay Mining, which plans to mine for copper, nickel, cobalt, zinc and ilmenite.

The receding of the ice sheet has opened additional land for exploration, Stensgaard said, and warmer weather has lengthened the season when ships can travel to the island without the risk of being frozen in. “I can put people in the field longer,” he said.

Having spent long months in tents doing geological fieldwork, he sees the transformation not just as an entrepreneur.

“I’ve seen glaciers disappear completely,” he said. “I’ve seen starving polar bears because of disappearing sea ice. These are personally disturbing changes.”

But, since the minerals he hopes to mine are critical for any future green-energy transition, climate change is creating opportunities in Greenland to address the reason it is melting.

For years, I saw myself not as a global-warming denier (a loaded term with its tendentious echo of Holocaust denial) but rather as an agnostic on the causes of climate change and a scoffer at the idea that it was a catastrophic threat to the future of humanity.

It’s not that I was unalterably opposed to the idea that, by pumping carbon dioxide into the atmosphere, modern civilization was contributing to the warming by 1 degree Celsius and the inches of sea-level rise the planet had experienced since the dawn of the industrial age. It’s that the severity of the threat seemed to me wildly exaggerated and that the proposed cures all smacked of old-fashioned statism mixed with new-age religion.

Hadn’t we repeatedly lived through previous alarms about other, allegedly imminent, environmental catastrophes that didn’t come to pass, like the belief, widespread in the 1970s , that overpopulation would inevitably lead to mass starvation? And if the Green Revolution had spared us from that Malthusian nightmare, why should we not have confidence that human ingenuity wouldn’t also prevent the parade of horribles that climate change was supposed to bring about?

I had other doubts, too. It seemed hubristic, or worse, to make multitrillion-dollar policy bets based on computer models trying to forecast climate patterns decades into the future. Climate activists kept promoting policies based on technologies that were either far from mature (solar energy) or sometimes actively harmful (biofuels).

Expensive efforts to curb greenhouse gas emissions in Europe and North America seemed particularly fruitless when China, India and other developing countries weren’t about to curb their own appetite for fossil fuels. There was also a millenarian fervor that bothered me about climate activism, with its apocalyptic imagery (the Statue of Liberty underwater ) and threats of doom unless we were willing to live far more frugally.

That was my frame of mind when, in April 2017, I wrote my first column for The Times, “ Climate of Complete Certainty .” The blowback was intense. Climate scientists denounced me in open letters; petitions were circulated demanding that I be fired. The response mainly hardened my conviction that climate activists were guilty of precisely what I charged them with: intellectual self-certainty that is often a prescription for disaster.

Among the signatories of one petition was an oceanographer, John Englander, who runs an educational and advocacy group, the Rising Seas Institute . Two years later, on a visit to New York, he wrote me out of the blue and asked to meet. Unlike most of my detractors, his note was so cordial that it seemed churlish to say no. We met the next day.

Englander is a trim, affable and eloquent man of 72 who once ran the Cousteau Society and reminds me of a bearded Patrick Stewart, albeit with an American accent. His pitch was simple: The coastline we have taken for granted for thousands of years of human history changed rapidly in the past on account of natural forces — and would soon be changing rapidly and disastrously by man-made ones. A trip to Greenland, which holds one-eighth of the world’s ice on land (most of the rest is in Antarctica) would show me just how drastic those changes have been. Would I join him?

Again, it seemed churlish to say no (though the pandemic would delay my trip by two years). More to the point, if my main objection to the climate activists was my impression of their overweening certitude, didn’t it behoove me to check my own? Where — except in the risk of changing my mind — was the harm in testing my views?

From a jetliner , the most striking features of Greenland seem to be its vastness and its blankness, which put me in mind of a line from Robert Frost’s poem “Desert Places”: “A blanker whiteness of benighted snow/With no expression, nothing to express.” It was only when I got to the sheet itself that I realized the line could not be less apt. Trapped in the whiteness was a story about the world’s distant past and potential future.

Greenland is about the size of Alaska and California combined and, except at its coasts, is covered by ice that in places is nearly two miles thick. Even that’s only a fraction of the ice in Antarctica, which is more than six times as large. But the Arctic is warming at nearly four times the global average, meaning Greenland’s ice also poses a nearer-term risk because it is melting faster. If all its ice were to melt, global sea levels would rise by some 24 feet. That would be more than enough to inundate hundreds of coastal cities in scores of nations, from Jakarta and Bangkok to Copenhagen and Amsterdam to Miami and New Orleans.

But just how fast is Greenland’s ice melting right now? Is this an emergency for our time, or is it a problem for the future?

Measuring ice loss on scales so vast is no easy task, since Greenland, like a spendthrift billionaire, is both constantly accumulating and shedding almost unfathomable quantities of ice over long spans of time. But scientists have been drilling ice-core samples from Greenland for decades, giving them a very good idea of climatic changes stretching back thousands of years. Better yet, a pair of satellites that detect anomalies in Earth’s gravity fields has been taking measurements of the sheet regularly for nearly 20 years, giving scientists a much more precise idea of what is happening.

The data shows unmistakably that Greenland’s ice is not in balance. It is losing far more than it is gaining.

From April 2002 to July 2022, Greenland has lost more than 5,000 gigatons of ice to the ocean

Ice mass change

relative to 2002

–5 meters of ice

–5 meters

In Copenhagen before my departure for Greenland, I chatted with Liam Colgan, a Canadian research climatologist with the Geological Survey of Denmark and Greenland. “We haven’t had a good positive mass balance year since the late 1990s,” he told me in a follow-on email when I asked him to explain the data for me. The losses can vary sharply by year. The annualized average over the past 30 years, he added, is 170 gigatons per year. That’s the equivalent of about 5,400 tons of ice loss per second. That “suggests that Greenland ice loss has been tracking the I.P.C.C. worse-case, highest-carbon-emission scenario.” (The Intergovernmental Panel on Climate Change is the U.N. body that assesses climate change.)

Still, it’s hard to forecast with any precision what that means. “Anyone who says they know what the sea level is going to be in 2100 is giving you an educated guess,” said NASA’s Willis. “The fact is, we’re seeing these big ice sheets melt for the first time in history, and we don’t really know how fast they can go.”

His own educated guess: “By 2100, we are probably looking at more than a foot or two and hopefully less than seven or eight feet. But we are struggling to figure out just how fast the ice sheets can melt. So the upper end of range is still not well known.”

On the face of it, that sounds manageable. Even if sea levels rise by eight feet, won’t the world have nearly 80 years to come to grips with the problem, during which technologies that help us mitigate the effects of climate change while adapting to its consequences are likely to make dramatic advances? Won’t the world — including countries that today are poor — become far richer and thus more capable of weathering the floods, surges and superstorms?

Englander isn’t at all sanguine. The average rate at which sea level is rising around the world, he estimates, has more than tripled over the past three decades, to five millimeters a year from 1.5 millimeters. That may still seem minute, yet as the world learned during the pandemic, exponential increases have a way of hitting hard.

“When something is on a straight line or a smooth curve, you can plot its trajectory,” Englander said. “But sea level, like earthquakes and mudslides, is something that happens irregularly and can change rather quickly and surprise us. The point is, you can no longer predict the future by the recent past.”

Another major wild card is Antarctica, where the average rate of ice mass loss is more than 150 gigatons a year. Shortly after I returned from Greenland, a glacier in West Antarctica called Thwaites, roughly the size of Florida, caught the world’s attention when a study suggested it was, according to a co-author, Robert Larter of the British Antarctic Survey, “holding on today by its fingernails.”

Or was that alarmist? In The Wall Street Journal’s editorial pages, where I used to work, the theoretical physicist Steven Koonin, a former under secretary for science in the Obama administration’s Energy Department, cast doubt on the threat from Thwaites in a voice that could have once been mine. He also thinks the risks associated with Greenland’s melting are less a product of human-induced global warming than of natural cycles in North Atlantic currents and temperatures, which over time have a way of regressing to the mean.

“Much climate reporting today highlights short-term changes when they fit the narrative of a broken climate but then ignores or plays down changes when they don’t, often dismissing them as ‘just weather,’” he wrote in February .

Another climate nonalarmist is Roger Pielke Jr., a professor of environmental studies at the University of Colorado Boulder. I call Pielke a nonalarmist rather than a skeptic because he readily acknowledges that the challenges associated with climate change, including sea-level rise, are real, serious and probably unstoppable, at least for many decades.

But that is also the source of his (relative) optimism. “If we have to have a problem,” he told me when I reached him by phone, “we probably want one with a slow onset that we can see coming. It’s not like an asteroid coming from space.”

Among Pielke’s areas of expertise is the analysis of long-term trends in weather and climate-related disasters. Even as the nominal cost of hurricanes, floods, fires and droughts has grown, the economic impact of these disasters relative to the overall size of the economy continues to fall, a function of better forecasting, infrastructure, planning and responsiveness when disaster strikes — all of which, in turn, are the result of the massive increase in wealth the world has enjoyed in the past century.

“Since the 1940s, the impact of floods as a proportion of U.S. gross domestic product has dropped by 70 percent-plus, ” Pielke said. “We see this around the world, across phenomena. The story is that fewer people are dying and we are having less damage proportional to G.D.P.”

A considerable amount of data bears Pielke out . In the 1920s, the estimated average annual death toll from natural catastrophes around the globe averaged more than 500,000 a year. The 1931 China floods alone killed as many as four million people not only through drowning but also by exposure, disease and famine. A more recent example, the 1970 Bhola cyclone, killed as many as half a million people in what is now Bangladesh.

In the 2010s, the annual average death toll was below 50,000 — a tenth of what it was a century ago. Hurricane Ian, among the strongest storms ever to hit Florida, had a death toll of at least 119 , a small fraction of the 8,000 believed killed by the Great Galveston hurricane of 1900

Even the poorest countries , while still unacceptably vulnerable, are suffering far fewer human and economic losses to climate-related disasters.

Global warming is real and getting worse, Pielke said, yet still it’s possible that humanity will be able to adapt to, and compensate for, its effects.

The death rate from natural disasters has fallen globally

Average number of deaths per 100,000 people, by decade.

Or maybe not. A few years ago, I would have found voices like Koonin’s and Pielke’s persuasive. Now I’m less sure. What intervened was a pandemic.

Just as I had once scoffed at the idea of climate doom, I had also, for almost identical reasons, dismissed predictions of another catastrophic pandemic on a par with the 1918-20 influenza outbreak. After all, hadn’t we pushed through previous alarms involving Ebola, SARS, MERS and vCJD (mad cow disease) without immense loss of life? Hadn’t virology, epidemiology, public hygiene, drug development and medicine all come a long way since the end of World War I, rendering comparisons with past pandemics mostly moot?

That’s what I thought until the spring of 2020, when, along with everyone else, I experienced how swiftly and implacably nature can overwhelm even the richest and most technologically advanced societies. It was a lesson in the sort of intellectual humility I recommended for others and began to realize I could use more of myself.

It was also a lesson in thinking about risk, especially those in the category known as high-impact, low-probability events that seem to be hitting us with such regularity in this century: the attacks of Sept. 11, 2001; the tsunamis of 2004 and 2011, the mass upheavals in the Arab world that began with a Tunisian street vendor’s self-immolation.

Here were some questions that gnawed at me: What if the past does nothing to predict the future? What if climate risks do not evolve gradually and relatively predictably but instead suddenly soar uncontrollably? How much lead time is required to deal with something like sea-level rise? How do we weigh the risks of underreacting to climate change against the risks of overreacting to it?

I called Seth Klarman, one of the world’s most successful hedge-fund managers , to think through questions of risk. While he’s not an expert on climate change, he has spent decades thinking deeply about every manner of risk. He’s also one of the rare people with a capacity to change his mind — including, he readily acknowledges, about climate risk. “I’ve talked to so many experts and seen so much evidence,” he told me over Zoom, “I’m convinced the climate is changing, and addressing climate change has become a philanthropic priority of mine.”

“If you face something that is potentially existential,” he explained, “existential for nations, even for life as we know it, even if you thought the risk is, say, 5 percent, you’d want to hedge against it.”

“One thing we try to do,” he said, “is we buy protection when it’s really inexpensive, even when we think we may well not need it.” The forces contributing to climate change, he noted, echoing Englander, “might be irreversible sooner than the damage from climate change has become fully apparent. You can’t say it’s far off and wait when, if you had acted sooner, you might have dealt with it better and at less cost. We have to act now.”

In other words, an ounce of prevention is worth a pound of cure. That’s particularly true if climate change is akin to cancer — manageable or curable in its earlier stages, disastrous in its later ones.

For Klarman, the simplest and most obvious climate hedge is a carbon tax. By “raising the price of oil, gas and coal to make alternative energy more economically attractive,” he said, “capitalists will be incentivized to act.”

Klarman recognizes that such a tax is easier said than done because, if it’s enacted by only a few nations, it becomes more of a form of virtue signaling than a serious climate change policy. Carbon taxes also tend to impose their burdens inequitably, favoring city dwellers over exurban and rural ones, knowledge businesses over manufacturers.

There’s a reason Barack Obama rejected a carbon tax, knowing it could be deeply unpopular among voters, and why France’s carbon tax sparked the “ yellow vest ” public revolt that has energized the far right.

As I’ve always believed, knowing there is grave risk to future generations — and expecting current ones to make immediate sacrifices for it — defies most of what we know about human nature. So I began to think more deeply about that challenge, and others.

When I had dinner with Stensgaard, the mining executive, he mentioned a statistic that stunned me. For the world to achieve the net-zero goal for carbon dioxide emissions by 2050, according to the International Energy Agency , we will have to mine, by 2040, six times the current amounts of critical minerals — nickel, cobalt, copper, lithium, manganese, graphite, chromium, rare earths and other minerals and elements — needed for electric vehicles, wind turbines and solar panels. And we will almost certainly have to do it from sources other than Russia, China, the Democratic Republic of Congo and other places that pose unacceptable strategic, environmental or humanitarian risks.

To bring carbon emissions to net zero, the world needs significantly more minerals

Global demand for minerals like copper, nickel, lithium and graphite, by type of clean energy.

What we used

What we’ll

need in 2040

Electric vehicles

and batteries

54x as many

0.4 million tons of minerals

Electricity

The I.E.A. estimates that the world will need three times as many minerals for its electricity networks in 2040 to meet net zero.

Electric vehicles and batteries

Electricity networks

That should be great news for people like Stensgaard — provided Greenlanders are willing to go along . Across the iceberg-strewn bay from where we dined lies Disko Island, twice the size of Long Island and home to around 1,000 people. According to Stensgaard, it is believed to contain 12 million to 16 million tons of nickel. To put that figure in perspective, Stensgaard told me that according to one estimate, the Norilsk nickel mine in Russia, one of the largest in the world, has produced about 8.3 million tons since the 1940s.

A world committed to net zero will need many more Disko Islands to supply its “clean” energy needs. I put the word “clean” in quotation marks because the term is a misnomer. As in everything else in life, so too with the environment: There is no such thing as a free lunch. Whether it’s nuclear, biofuels, natural gas, hydroelectric or, yes, wind and solar, there will always be serious environmental downsides to any form of energy when used on a massive scale. A single industrial-size wind turbine , for instance, typically requires about a ton of rare earth metals as well as three metric tons of copper, which is notoriously destructive and dirty to mine .

Just as significantly, as I’ve long believed, no “clean energy” solution will easily liberate us from our overwhelming and, for now, inescapable dependence on fossil fuels.

Nobody brings the point home better than Vaclav Smil , the Canadian polymath whose most recent book, “How the World Really Works,” should be required reading for policymakers and anyone else interested in a serious discussion about potential climate solutions.

Many people tend to think of fossil fuels mostly in terms of transportation, electrical generation and heating. But how often do we consider the necessity of fossil fuels in the production of nitrogen fertilizer, without which, Smil noted, “it would be impossible to feed at least 40 percent and up to 50 percent of today’s nearly eight billion people”? It’s difficult to imagine modern life without plastics, made mainly from the hydrocarbons ethylene and propylene, or steel, made with coking coal and natural gas, or cement or asphalt.

Some critics respond to Smil’s arguments with a type of heroic optimism that borders on magical thinking. Why, they ask, can’t we do more to grow our food organically and distribute and consume it locally? The only way we could do that and make a meaningful difference for the climate is if millions of us returned to farming, while accepting a world that can feed far fewer people. Or they cheer investments in wind and solar power without adequately considering that merely increasing the supply of renewable energy does very little to diminish a continued overall demand for fossil fuels, because we have yet to solve the intermittence problem : The sun doesn’t always shine, the wind doesn’t always blow, and we haven’t figured out how to store extra energy at the necessary scale.

The poster child for this kind of magical thinking is Germany, which undertook a historic Energiewende — “energy revolution” — only to come up short. At the turn of the century, Germany got about 85 percent of its primary energy from fossil fuels. Now it gets about 78 percent, a puny reduction, considering that the country has spent massive sums on renewables to increase the share of electricity it generates from them.

What went wrong? Many things, not least Angela Merkel’s abrupt decision to shut down all of Germany’s nuclear power plants right after the Fukushima disaster of 2011. That forced Germany to lean more heavily on coal, foreign oil and gas. Now Germany faces a winter with the prospect of uncertain energy supplies from its former partners in Moscow.

Things could turn a corner once scientists finally figure out a technical solution to the energy storage problem. Or when governments and local actors get over their NIMBYism when it comes to permitting and building a large energy grid to move electricity from Germany’s windy north to its energy-hungry south. Or when thoughtful environmental activists finally come to grips with the necessity of nuclear energy — one of the few energy sources, along with hydroelectric power, that combine reliability, energy density and no direct carbon emissions.

Till then, even as I’ve come to accept the danger we face, I think it’s worth extending the cancer metaphor a little further: Just as cancer treatments, when they work at all, can have terrible side effects, much the same can be said of climate treatments: The gap between an accurate diagnosis and effective treatment remains dismayingly wide. The problem has become clearer to me; the solution hasn’t.

Maybe, I realized, in assessing my newfound concerns about climate change, my long-held beliefs might provide a solution — look to the market.

The way we’ve dealt with other vast and persistent problems provides some lessons.

For many decades, the World Bank, International Monetary Fund, U.S. Agency for International Development and other agencies, foreign and domestic, pumped trillions of dollars into some of the world’s poorest countries, with ingenious development schemes that fell apart on contact with local realities. The developing world got stuck in debt traps, aid-fueled corruption and debilitating cycles of dependency.

Only when countries like Vietnam and China turned to a different model, of largely bottom-up, market-driven development, did hundreds of millions of people get lifted out of destitution.

Or consider another remarkable fact noted by Smil: In the United States, the difference between total water consumption in 1965 and 2015 is less than 4 percent. In the same span of time, population grew by more than 60 percent.

Laws, regulations and growing environmental awareness played important roles. So did increasing urbanization: More people living in apartments means fewer lawns that need to be watered.

But the most important transformation has come in agriculture, which uses about 70 percent of the world’s freshwater supply.

Farmers gradually adopted sprinkler and drip irrigation systems, rather than more wasteful flood irrigation, not to conserve water but because the technology provided higher crop yields and larger profit margins.

Water shortages “will spur a revolutionary, aggressive approach to getting rid of flood irrigation,” said Seth Siegel, the chief sustainability officer of the Israeli AgTech company N-Drip . “Most of this innovation will be driven by free-market capitalism, with important incentives from government and NGOs.”

Despite noble intentions, climate-change action has too often involved top-down plans with grandiose ambitions and poor execution.

There was a time when Al Gore was emphatically in favor of ethanol, support that George W. Bush later made his own through the 2005 Renewable Fuel Standard. It is now widely acknowledged to be an unmitigated failure , costing billions in regulatory compliance, but unkillable because of its popularity with farm-state politicians. Cap-and-trade systems were once touted as a market-friendly way to control carbon dioxide emissions. Yet from Europe to California to the agencies of the U.N. , bureaucrats and industry have consistently found ways to game or corrupt the trading of emissions permits. The 2015 Paris Agreement that the Biden administration rejoined with such fanfare sets highly ambitious targets for greenhouse gas reductions that burnish the environmental credentials of the governments that sign it. But the agreement has no enforcement mechanism, and the idea that countries like Russia, Saudi Arabia, China and India (which is growing more — not less — dependent on coal ) are going to meet their stated emissions targets is fanciful to the point of absurdity.

Yet meaningful environmental progress has been made through market forces. In this century, America’s carbon dioxide emissions across fuel types have fallen to well below 5,000 million metric tons per year, from a peak of about 6,000 million in 2007, even as our inflation-adjusted G.D.P. has grown by over 50 percent and total population by about 17 percent.

Renewables, particularly wind power, played a role. So did efficiency mandates.

Yet the biggest single driver in emissions reductions from 2005 to 2017 was the switch from coal to natural gas for power generation, since gas produces roughly half the carbon dioxide as coal. This, in turn, was the result of a fracking revolution in the past decade, fiercely resisted by many environmental activists, that made the United States the world’s largest gas producer. As with nuclear power, fracking carries real environmental risks (including methane emissions) that can’t be ignored. But anyone interested in useful solutions that significantly reduce emissions without incurring huge costs needs to not make the perfect the enemy of the good.

In the long run, we are likelier to make progress when we adopt partial solutions that work with the grain of human nature, not big ones that work against it. Sometimes those solutions will be legislative — at least when they nudge , rather than force, the private sector to move in the right direction. But more often they will come from the bottom up, in the form of innovations and practices tested in markets, adopted by consumers and continually refined by use. They may not be directly related to climate change but can nonetheless have a positive impact on it. And they probably won’t come in the form of One Big Idea but in thousands of little ones whose cumulative impacts add up.

On my last night in Greenland I took an evening boat ride through the enormous icebergs that had pushed their way out of the Ilulissat Icefjord and were now beginning to float free in the deep waters of Disko Bay. It is generally believed that one such iceberg made its way from the bay to a spot in the North Atlantic where it met the R.M.S. Titanic on the night of April 14, 1912, and sank it. It’s easy to get carried away with a metaphor, but it was hard not to think that Greenland could produce a similarly awful surprise, on a vastly greater scale, for an overconfident civilization that can’t bring itself to prepare adequately for the unthinkable moment when it could suddenly founder.

Except we are not that civilization.

The problem with our civilization isn’t overconfidence. It’s polarization, paralysis and a profound lack of trust in all institutions, including the scientific one (another pandemic-era lesson). Devising effective climate policies begins with recognizing the reality of the social and political landscape in which all policy operates. Some thoughts on how we might do better:

1) Engagement with critics is vital. Insults and stridency are never good tools of persuasion, and trying to cow or censor climate skeptics into silence rarely works. Englander got a lot further with me by saying, “Let’s talk,” than by signing a letter saying, in effect, “Shut up.” I too might have spared myself the outraged reception to my first column if it hadn’t been preceded by the name-calling of my old columns — such as when I called climate activists “a caste of spectacularly unattractive people pretending to an obscure form of knowledge that promises to make the seas retreat and the winds abate.”

2) Separate facts from predictions and predictions from policy . Global warming is a fact. So is the human contribution to it. So are observed increases in temperature and sea levels. So are continued increases if we continue to do more of the same. But the rate of those increases is difficult to predict even with the most sophisticated computer modeling. The scientific establishment would do more to enhance trust if it communicated what it isn’t sure of — like the relation between climate change and specific extreme weather events — as much as what it is. It would enhance it even further if climate scientists did not use the authority of their field to push for policies whose economic, political and social implications they might not fully understand.

3) Don’t allow climate to become a mainly left-of-center concern. One reason the topic of climate has become so anathema to many conservatives is that so many of the proposed solutions have the flavor, and often the price tag, of old-fashioned statism. But climate is a universally shared good and ought to be a truly common interest. Conservatives can do a lot more to develop their own set of realistic policy prescriptions (for instance, expedited permitting and tax breaks for next-generation nuclear energy). But first, many of them have to be brought around, as I was this year, about the need for action.

4) Be honest about the nature of the challenge. Talk of an imminent climate catastrophe is probably misleading, at least in the way most people understand “imminent.” A continual drumbeat of alarm may do more to exhaust voters than it will to rouse them. A more accurate description of the challenge might be a “potentially imminent tipping point,” meaning the worst consequences of climate change can still be far off but the end of our ability to reverse them is drawing near. Again, the metaphor of cancer — never safe to ignore and always better to deal with at Stage 2 than at Stage 4 — can be helpful.

5) Be humble about the nature of the solutions. The larger the political and financial investment in a “big fix” response to climate change on the scale of the Energiewende, the greater the loss in time, capital and (crucially) public trust when it doesn’t work as planned. Sometimes it pays to think small. As Smil noted, we can also do a lot of good by requiring triple-pane windows and proper insulation to make homes that are often likely to stand for 100 years vastly more energy efficient in cold winters and hot summers. A shift away from S.U.V.s — the ubiquity of which is a perverse outgrowth of 1970s-era fuel efficiency standards that created exemptions for light trucks — would be another quiet but major advance.

6) Begin solving problems our great-grandchildren will face. Start with sea-level rise: We cannot move Miami or Kolkata anytime soon, if ever. But we can act immediately to preserve more of our shoreline from further development and urbanization. We can also stop providing incentives for building in flood-prone areas by raising the price of federal flood insurance to reflect the increased risk more accurately.

7) Stop viewing economic growth as a problem. Industrialization may be the leading cause of climate change. But we cannot and will not reverse it through some form of deindustrialization, which would send the world into poverty and deprivation. Instead, economic growth should be seen as an ally in the fight against climate change, because it creates both the wealth that can mitigate the effects of climate change and the technological innovation needed to address its causes. That’s especially true of poorer countries, for which foreign investment, free trade, market-oriented reforms and good regulatory frameworks will do more to build climate resilience than additional billions in foreign aid.

8) Get serious about the environmental trade-offs that come with clean energy . You cannot support wind farms but hinder the transmission lines needed to bring their power to the markets where they are needed. You cannot support wind farms but sue to block them in places where they might block your view of Nantucket Sound. You cannot support wind farms but support environmental regulations that make mining for rare earths in the United States unprofitable and send the industry to China (where meaningful regulations are effectively nonexistent). And you cannot cheer U.S. reductions in greenhouse gas emissions but oppose the fracking revolution in natural gas that helped bring it about.

9) A problem for the future is, by its very nature, a moral one. A conservative movement that claims to care about what we owe the future has the twin responsibility of setting an example for its children and at the same time preparing for that future. The same prudential logic that applies to personal finances, business decisions, Social Security, the federal debt or other risks to financial solvency should dictate thoughtful policies when it comes to climate.

I arrived in Greenland thinking about Robert Frost’s “Desert Places.” When I left, the verses I had in mind were from “God’s Grandeur,” a poem by Gerard Manley Hopkins that my father had me memorize as a boy:

Generations have trod, have trod, have trod;

And all is seared with trade; bleared, smeared with toil;

And wears man’s smudge and shares man’s smell: the soil

Is bare now, nor can foot feel, being shod.

And for all this, nature is never spent;

There lives the dearest freshness deep down things;

And though the last lights off the black West went

Oh, morning, at the brown brink eastward, springs —

Because the Holy Ghost over the bent

World broods with warm breast and with ah! bright wings.

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Climate Change: Evidence and Causes: Update 2020 (2020)

Chapter: conclusion, c onclusion.

This document explains that there are well-understood physical mechanisms by which changes in the amounts of greenhouse gases cause climate changes. It discusses the evidence that the concentrations of these gases in the atmosphere have increased and are still increasing rapidly, that climate change is occurring, and that most of the recent change is almost certainly due to emissions of greenhouse gases caused by human activities. Further climate change is inevitable; if emissions of greenhouse gases continue unabated, future changes will substantially exceed those that have occurred so far. There remains a range of estimates of the magnitude and regional expression of future change, but increases in the extremes of climate that can adversely affect natural ecosystems and human activities and infrastructure are expected.

Citizens and governments can choose among several options (or a mixture of those options) in response to this information: they can change their pattern of energy production and usage in order to limit emissions of greenhouse gases and hence the magnitude of climate changes; they can wait for changes to occur and accept the losses, damage, and suffering that arise; they can adapt to actual and expected changes as much as possible; or they can seek as yet unproven “geoengineering” solutions to counteract some of the climate changes that would otherwise occur. Each of these options has risks, attractions and costs, and what is actually done may be a mixture of these different options. Different nations and communities will vary in their vulnerability and their capacity to adapt. There is an important debate to be had about choices among these options, to decide what is best for each group or nation, and most importantly for the global population as a whole. The options have to be discussed at a global scale because in many cases those communities that are most vulnerable control few of the emissions, either past or future. Our description of the science of climate change, with both its facts and its uncertainties, is offered as a basis to inform that policy debate.

A CKNOWLEDGEMENTS

The following individuals served as the primary writing team for the 2014 and 2020 editions of this document:

• Eric Wolff FRS, (UK lead), University of Cambridge
• Inez Fung (NAS, US lead), University of California, Berkeley
• Brian Hoskins FRS, Grantham Institute for Climate Change
• John F.B. Mitchell FRS, UK Met Office
• Tim Palmer FRS, University of Oxford
• Benjamin Santer (NAS), Lawrence Livermore National Laboratory
• John Shepherd FRS, University of Southampton
• Keith Shine FRS, University of Reading.
• Susan Solomon (NAS), Massachusetts Institute of Technology
• Kevin Trenberth, National Center for Atmospheric Research
• John Walsh, University of Alaska, Fairbanks
• Don Wuebbles, University of Illinois

Staff support for the 2020 revision was provided by Richard Walker, Amanda Purcell, Nancy Huddleston, and Michael Hudson. We offer special thanks to Rebecca Lindsey and NOAA Climate.gov for providing data and figure updates.

The following individuals served as reviewers of the 2014 document in accordance with procedures approved by the Royal Society and the National Academy of Sciences:

• Richard Alley (NAS), Department of Geosciences, Pennsylvania State University
• Alec Broers FRS, Former President of the Royal Academy of Engineering
• Harry Elderfield FRS, Department of Earth Sciences, University of Cambridge
• Joanna Haigh FRS, Professor of Atmospheric Physics, Imperial College London
• Isaac Held (NAS), NOAA Geophysical Fluid Dynamics Laboratory
• John Kutzbach (NAS), Center for Climatic Research, University of Wisconsin
• Jerry Meehl, Senior Scientist, National Center for Atmospheric Research
• John Pendry FRS, Imperial College London
• John Pyle FRS, Department of Chemistry, University of Cambridge
• Gavin Schmidt, NASA Goddard Space Flight Center
• Emily Shuckburgh, British Antarctic Survey
• Gabrielle Walker, Journalist
• Andrew Watson FRS, University of East Anglia

The Support for the 2014 Edition was provided by NAS Endowment Funds. We offer sincere thanks to the Ralph J. and Carol M. Cicerone Endowment for NAS Missions for supporting the production of this 2020 Edition.

F OR FURTHER READING

For more detailed discussion of the topics addressed in this document (including references to the underlying original research), see:

• Intergovernmental Panel on Climate Change (IPCC), 2019: Special Report on the Ocean and Cryosphere in a Changing Climate [ https://www.ipcc.ch/srocc ]
• National Academies of Sciences, Engineering, and Medicine (NASEM), 2019: Negative Emissions Technologies and Reliable Sequestration: A Research Agenda [ https://www.nap.edu/catalog/25259 ]
• Royal Society, 2018: Greenhouse gas removal [ https://raeng.org.uk/greenhousegasremoval ]
• U.S. Global Change Research Program (USGCRP), 2018: Fourth National Climate Assessment Volume II: Impacts, Risks, and Adaptation in the United States [ https://nca2018.globalchange.gov ]
• IPCC, 2018: Global Warming of 1.5°C [ https://www.ipcc.ch/sr15 ]
• USGCRP, 2017: Fourth National Climate Assessment Volume I: Climate Science Special Reports [ https://science2017.globalchange.gov ]
• NASEM, 2016: Attribution of Extreme Weather Events in the Context of Climate Change [ https://www.nap.edu/catalog/21852 ]
• IPCC, 2013: Fifth Assessment Report (AR5) Working Group 1. Climate Change 2013: The Physical Science Basis [ https://www.ipcc.ch/report/ar5/wg1 ]
• NRC, 2013: Abrupt Impacts of Climate Change: Anticipating Surprises [ https://www.nap.edu/catalog/18373 ]
• NRC, 2011: Climate Stabilization Targets: Emissions, Concentrations, and Impacts Over Decades to Millennia [ https://www.nap.edu/catalog/12877 ]
• Royal Society 2010: Climate Change: A Summary of the Science [ https://royalsociety.org/topics-policy/publications/2010/climate-change-summary-science ]
• NRC, 2010: America’s Climate Choices: Advancing the Science of Climate Change [ https://www.nap.edu/catalog/12782 ]

Much of the original data underlying the scientific findings discussed here are available at:

• https://data.ucar.edu/
• https://climatedataguide.ucar.edu
• https://iridl.ldeo.columbia.edu
• https://ess-dive.lbl.gov/
• https://www.ncdc.noaa.gov/
• https://www.esrl.noaa.gov/gmd/ccgg/trends/
• http://scrippsco2.ucsd.edu
• http://hahana.soest.hawaii.edu/hot/

Climate change is one of the defining issues of our time. It is now more certain than ever, based on many lines of evidence, that humans are changing Earth's climate. The Royal Society and the US National Academy of Sciences, with their similar missions to promote the use of science to benefit society and to inform critical policy debates, produced the original Climate Change: Evidence and Causes in 2014. It was written and reviewed by a UK-US team of leading climate scientists. This new edition, prepared by the same author team, has been updated with the most recent climate data and scientific analyses, all of which reinforce our understanding of human-caused climate change.

Scientific information is a vital component for society to make informed decisions about how to reduce the magnitude of climate change and how to adapt to its impacts. This booklet serves as a key reference document for decision makers, policy makers, educators, and others seeking authoritative answers about the current state of climate-change science.

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The climate is changing, but not just because of humans. Here's why that matters.

The climate is changing — the thing is, it isn’t just due to humans.

Natural forces beyond human control are also gradually affecting our climate. These geophysical forces are vital to understanding global warming. Man is indeed responsible for a large portion — possibly even a majority — of global warming. But also in play are complex gravitational interactions, including changes in the Earth’s orbit, axial tilt and torque.

This fact needs to be included in the public debate. Because these gravitational shifts, occurring over millennia, can influence climate patterns and ultimately lead to noticeable variations in seasons. Interestingly, research suggests climate change can alter the tilt of the Earth, but an unrelated change in tilt can also further change the climate. It is a balance-counterbalance relationship.

Changes in the Earth’s path around the Sun, or eccentricity, involve shifts in the orbit around the Sun from a roughly circular journey to more of an elliptical one . When the Earth gradually adopts a more elliptical orbit, there are more pronounced temperatures during the summer and winter months. This alteration is exacerbated when the Earth’s axial tilt is inclined to a sharper degree than usual. As this happens, it causes the North and South Poles to be positioned more directly toward the Sun.

Haven’t you noticed the recent rise in irregular weather patterns? This is not just a man-made problem. Gradual slight variations in the Earth’s orbit around the Sun can strongly influence temperature extremes. This is important because the conversation around climate change has become so politicized, we've totally lost sight of the science — and with it, any room for bipartisanship.

Tropical storms, for example, have been forming later in what we know as hurricane season. Based on my own analysis, over the past three decades, the majority of Category 3 or stronger storms to hit the United States appear from late August to early October. Earlier in the 20th century, storms usually occurred in June, July and early August.

It doesn’t stop there. Changes in seasons can also affect other types of storms, including severe winter snowstorms and tornadoes. Recall the Storm of the Century in 1993 on the heels of Hurricane Andrew the year prior. Or what about the recent string of snowstorms (with names like Snowpocalypse, Snowmageddon and Snowzilla) dovetailing with warm-weather superstorms. Climate extremes are evident, and not just with hurricanes.

The variations in the Earth’s orbit are known as the Milankovitch cycles — after the Serbian geophysicist Milutin Milanković, who hypothesized this phenomenon in the 1920s. He discovered that variations in the Earth’s path around the Sun, axial tilt and torque could together affect our climate.

Even a slight change or orientation in the precession of the Earth’s rotating body can cause a wobbling effect shifting torque in different areas since the planet is not a perfect sphere to some people’s surprise.

Now would seem a particularly apt time to act. The 2017 Atlantic hurricane season was an intense, record-setting period . With several landfall hurricanes — Harvey, Irma, Jose and Maria — barreling their way through the Caribbean and Gulf of Mexico, devastating parts of the Leeward Islands and United States.

Still, even President Donald J. Trump has implied the whole of idea climate change may just be a hoax . Most Republicans seem to agree that it is not a serious problem.

Meanwhile, while some Democrats have tried to use the frequency and intensity of storms in the hopes of highlighting the climate change conversation, even this effort has seemed muted.

To make effective policy, it is important for politicians and activists alike to set aside their ideological differences.

There is now a real opportunity for new legislation, sound environmental legislation. But will we squander this unprecedented opportunity, punting the ball yet again? You can bet on it. Given the realities of everyday life, the extent of social beliefs, political attitudes and economic perspectives vary on a wide range of policy issues.

To make sound and effective policy, it is important for politicians and activists alike to set aside their ideological differences and return to the basics of science, in this case, the mechanics of science. After all, shouldn’t we be relying more heavily upon geoscientists and weather forecasters to provide evidence-based data and predictive modeling?

Risks to disasters are increasing. Population growth along coastlines worldwide, in addition to technological and infrastructural development, will inherently result in a concomitant increase in places prone to disasters. Modern society relies upon government for effective response to and recovery from such events.

Change is occurring and will continue to do so. As the population continues to explode and resources are consumed on a massive scale, trying to stop both is unrealistic. It is more than just being unrealistic, it is simply wasting critical time. I know, science isn’t sexy. The obsession on why storms are occurring in lieu of discussing the how is leading us down a dangerous path. A deadly path.

The heightened culture of disaster only feeds our attention on political banter and ideological semantics with no room for informed decision-making.

We get it, Mother Nature always wins. So, are we now faced with the sobering lesson that little can be done, and we should just throw in the towel? No, of course not. Though climate change is inevitable, we also need to have a healthy appreciation of the fact that climate shifts aren’t just limited to rapidly changing weather patterns.

Turning the corner into unexplored territory is always difficult. By having a broader sense of communal resiliency — social, political and economic standing — we can manage this unavoidable pendulum of climate extremes. With the recent sweeping of storms draining response efforts and budgetary resources, now is the time to set aside the theatrical shenanigans and engage in realpolitik.

Tonya T. Neaves is the director for the Centers on the Public Service at George Mason University’s Schar School of Policy and Government, where she also is a faculty member in its master of public administration program and coordinator for the Emergency Management and Homeland Security certificate.

Tonya T. Neaves is the director for the Centers on the Public Service at George Mason University’s Schar School of Policy and Government, where she also is a faculty member in its master of public administration program and coordinator for the Emergency Management and Homeland Security certificate. 

• ENVIRONMENT

What is global warming, explained

The planet is heating up—and fast.

Glaciers are melting , sea levels are rising, cloud forests are dying , and wildlife is scrambling to keep pace. It has become clear that humans have caused most of the past century's warming by releasing heat-trapping gases as we power our modern lives. Called greenhouse gases, their levels are higher now than at any time in the last 800,000 years .

We often call the result global warming, but it is causing a set of changes to the Earth's climate, or long-term weather patterns, that varies from place to place. While many people think of global warming and climate change as synonyms , scientists use “climate change” when describing the complex shifts now affecting our planet’s weather and climate systems—in part because some areas actually get cooler in the short term.

Climate change encompasses not only rising average temperatures but also extreme weather events , shifting wildlife populations and habitats, rising seas , and a range of other impacts. All of those changes are emerging as humans continue to add heat-trapping greenhouse gases to the atmosphere, changing the rhythms of climate that all living things have come to rely on.

What will we do—what can we do—to slow this human-caused warming? How will we cope with the changes we've already set into motion? While we struggle to figure it all out, the fate of the Earth as we know it—coasts, forests, farms, and snow-capped mountains—hangs in the balance.

Understanding the greenhouse effect

The "greenhouse effect" is the warming that happens when certain gases in Earth's atmosphere trap heat . These gases let in light but keep heat from escaping, like the glass walls of a greenhouse, hence the name.

Sunlight shines onto the Earth's surface, where the energy is absorbed and then radiate back into the atmosphere as heat. In the atmosphere, greenhouse gas molecules trap some of the heat, and the rest escapes into space. The more greenhouse gases concentrate in the atmosphere, the more heat gets locked up in the molecules.

Scientists have known about the greenhouse effect since 1824, when Joseph Fourier calculated that the Earth would be much colder if it had no atmosphere. This natural greenhouse effect is what keeps the Earth's climate livable. Without it, the Earth's surface would be an average of about 60 degrees Fahrenheit (33 degrees Celsius) cooler.

A polar bear stands sentinel on Rudolf Island in Russia’s Franz Josef Land archipelago, where the perennial ice is melting.

In 1895, the Swedish chemist Svante Arrhenius discovered that humans could enhance the greenhouse effect by making carbon dioxide , a greenhouse gas. He kicked off 100 years of climate research that has given us a sophisticated understanding of global warming.

Levels of greenhouse gases have gone up and down over the Earth's history, but they had been fairly constant for the past few thousand years. Global average temperatures had also stayed fairly constant over that time— until the past 150 years . Through the burning of fossil fuels and other activities that have emitted large amounts of greenhouse gases, particularly over the past few decades, humans are now enhancing the greenhouse effect and warming Earth significantly, and in ways that promise many effects , scientists warn.

Aren't temperature changes natural?

Human activity isn't the only factor that affects Earth's climate. Volcanic eruptions and variations in solar radiation from sunspots, solar wind, and the Earth's position relative to the sun also play a role. So do large-scale weather patterns such as El Niño .

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But climate models that scientists use to monitor Earth’s temperatures take those factors into account. Changes in solar radiation levels as well as minute particles suspended in the atmosphere from volcanic eruptions , for example, have contributed only about two percent to the recent warming effect. The balance comes from greenhouse gases and other human-caused factors, such as land use change .

The short timescale of this recent warming is singular as well. Volcanic eruptions , for example, emit particles that temporarily cool the Earth's surface. But their effect lasts just a few years. Events like El Niño also work on fairly short and predictable cycles. On the other hand, the types of global temperature fluctuations that have contributed to ice ages occur on a cycle of hundreds of thousands of years.

For thousands of years now, emissions of greenhouse gases to the atmosphere have been balanced out by greenhouse gases that are naturally absorbed. As a result, greenhouse gas concentrations and temperatures have been fairly stable, which has allowed human civilization to flourish within a consistent climate.

Greenland is covered with a vast amount of ice—but the ice is melting four times faster than thought, suggesting that Greenland may be approaching a dangerous tipping point, with implications for global sea-level rise.

Now, humans have increased the amount of carbon dioxide in the atmosphere by more than a third since the Industrial Revolution. Changes that have historically taken thousands of years are now happening over the course of decades .

Why does this matter?

The rapid rise in greenhouse gases is a problem because it’s changing the climate faster than some living things can adapt to. Also, a new and more unpredictable climate poses unique challenges to all life.

Historically, Earth's climate has regularly shifted between temperatures like those we see today and temperatures cold enough to cover much of North America and Europe with ice. The difference between average global temperatures today and during those ice ages is only about 9 degrees Fahrenheit (5 degrees Celsius), and the swings have tended to happen slowly, over hundreds of thousands of years.

But with concentrations of greenhouse gases rising, Earth's remaining ice sheets such as Greenland and Antarctica are starting to melt too . That extra water could raise sea levels significantly, and quickly. By 2050, sea levels are predicted to rise between one and 2.3 feet as glaciers melt.

As the mercury rises, the climate can change in unexpected ways. In addition to sea levels rising, weather can become more extreme . This means more intense major storms, more rain followed by longer and drier droughts—a challenge for growing crops—changes in the ranges in which plants and animals can live, and loss of water supplies that have historically come from glaciers.

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