Aridity appears to configure landscapes with a greater diversity of plant species that rely on symbiotic bacteria for nitrogen.
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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February 21, 2024
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Giant Locust Swarms Could Expand to New Areas With Climate Change, Study Suggests
In the coming decades, erratic periods of rain and drought could create new hot spots for the ravenous grasshoppers in west India and west central Asia, threatening crops and food security
February 21, 2024 9:10 a.m.
A 5,000-Pound Satellite Is Falling Back to Earth This Week—and Will Likely Land in the Ocean
The reentry of the satellite, called ERS-2, is part of an intentional effort by the European Space Agency to reduce orbital debris
February 20, 2024
New Satellite Will Track Methane Emissions From Space and Pinpoint Their Sources With A.I.
The mission, set to launch next month, comes as countries and fossil fuel companies pledge to reduce emissions of the powerful greenhouse gas
Climate Activists Stage Protest in Front of Botticelli's 'Birth of Venus'
Two men taped images of flooding in Tuscany to the Renaissance painting's protective glass
February 14, 2024
California Hammered by Heavy Rains, Mudslides in Devastating Atmospheric River Storms
Some areas received as much as 13 to 15 inches of rain over a five-day period as storms felled trees, destroyed homes and killed nine people
February 8, 2024
Earth Clocks Hottest January on Record, Marking 12 Months Above 1.5 Degree Celsius Warming Threshold
Though the world has not officially breached the Paris Agreement, the historic heat on land and at sea is a "significant milestone"
Ocean Sponge Skeletons Suggest a More Significant History of Global Warming Than Originally Thought
Analysis of the sea creatures’ skeletal chemistry suggests the world’s temperatures have increased by 1.7 degrees Celsius since pre-industrial times
February 7, 2024
Do We Need a Category 6 Designation for Hurricanes?
Global warming is leading to more intense storms well above the threshold for Category 5 hurricanes, scientists write in a new paper
February 6, 2024
Six Big Ways Climate Change Could Impact the United States by 2100
Climate change is expected to affect all parts of the country in the coming decades, threatening everything from our food supply to our coastlines
February 5, 2024
This Camera Is Taking a 1,000-Year-Long Exposure Photo of Tucson's Desert Landscape
Jonathon Keats, who devised the plan, hopes the camera will inspire onlookers to contemplate how humanity’s actions affect the environment
February 1, 2024
Plagues That Ravaged the Roman Empire Were Linked to Periods of Cold Weather
The changing climate may have had ripple effects that made people more susceptible to disease, new research suggests
January 30, 2024
These Paintings Reveal How the Dutch Adapted to Extreme Weather During the Little Ice Age
Artists like Pieter Bruegel the Elder and Hendrick Avercamp documented locals' resilience in the face of freezing winters and food shortages
Climate Activists Throw Soup at the 'Mona Lisa'
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January 29, 2024
Can Animals Evolve Fast Enough to Keep Up With Climate Change?
Some may be able to, while others may not
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Scientists Discover Four New Emperor Penguin Colonies From Satellite Images of Antarctica
The findings are a rare bright spot for the birds, which scientists predict will be mostly extinct by 2100
January 25, 2024
Doomsday Clock Stays at 90 Seconds to Midnight Amid Climate Change, War and A.I.
For the second year in a row, the clock is the nearest it has ever been to signaling our total annihilation
January 24, 2024
Could Sinking Tons of Seaweed to the Ocean Floor Help Combat Climate Change?
Submerged seaweed can store carbon at the bottom of the sea, but how effective the strategy will be remains unclear
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January 22, 2024
Seabed Trawling May Be Spewing Huge Amounts of CO2 Into the Atmosphere
New research suggests the controversial fishing method is also contributing to increased ocean acidification, which can harm marine wildlife
January 19, 2024
As the Planet Warms, Australia's Numbats Are at Risk of Overheating
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January 12, 2024
- Next ›
How global warming is disrupting life on Earth
The signs of global warming are everywhere, and are more complex than just climbing temperatures.
Our planet is getting hotter. Since the Industrial Revolution—an event that spurred the use of fossil fuels in everything from power plants to transportation—Earth has warmed by 1 degree Celsius, about 2 degrees Fahrenheit.
That may sound insignificant, but 2023 was the hottest year on record , and all 10 of the hottest years on record have occurred in the past decade.
Global warming and climate change are often used interchangeably as synonyms, but scientists prefer to use “climate change” when describing the complex shifts now affecting our planet’s weather and climate systems.
Climate change encompasses not only rising average temperatures but also natural disasters, shifting wildlife habitats, rising seas , and a range of other impacts. All of these changes are emerging as humans continue to add heat-trapping greenhouse gases , like carbon dioxide and methane, to the atmosphere.
What causes global warming?
When fossil fuel emissions are pumped into the atmosphere, they change the chemistry of our atmosphere, allowing sunlight to reach the Earth but preventing heat from being released into space. This keeps Earth warm, like a greenhouse, and this warming is known as the greenhouse effect .
Carbon dioxide is the most commonly found greenhouse gas and about 75 percent of all the climate warming pollution in the atmosphere. This gas is a product of producing and burning oil, gas, and coal. About a quarter of Carbon dioxide also results from land cleared for timber or agriculture.
Methane is another common greenhouse gas. Although it makes up only about 16 percent of emissions, it's roughly 25 times more potent than carbon dioxide and dissipates more quickly. That means methane can cause a large spark in warming, but ending methane pollution can also quickly limit the amount of atmospheric warming. Sources of this gas include agriculture (mostly livestock), leaks from oil and gas production, and waste from landfills.
What are the effects of global warming?
One of the most concerning impacts of global warming is the effect warmer temperatures will have on Earth's polar regions and mountain glaciers. The Arctic is warming four times faster than the rest of the planet. This warming reduces critical ice habitat and it disrupts the flow of the jet stream, creating more unpredictable weather patterns around the globe.
( Learn more about the jet stream. )
A warmer planet doesn't just raise temperatures. Precipitation is becoming more extreme as the planet heats. For every degree your thermometer rises, the air holds about seven percent more moisture. This increase in moisture in the atmosphere can produce flash floods, more destructive hurricanes, and even paradoxically, stronger snow storms.
The world's leading scientists regularly gather to review the latest research on how the planet is changing. The results of this review is synthesized in regularly published reports known as the Intergovernmental Panel on Climate Change (IPCC) reports.
A recent report outlines how disruptive a global rise in temperature can be:
- Coral reefs are now a highly endangered ecosystem. When corals face environmental stress, such as high heat, they expel their colorful algae and turn a ghostly white, an effect known as coral bleaching . In this weakened state, they more easily die.
- Trees are increasingly dying from drought , and this mass mortality is reshaping forest ecosystems.
- Rising temperatures and changing precipitation patterns are making wildfires more common and more widespread. Research shows they're even moving into the eastern U.S. where fires have historically been less common.
- Hurricanes are growing more destructive and dumping more rain, an effect that will result in more damage. Some scientists say we even need to be preparing for Cat 6 storms . (The current ranking system ends at Cat 5.)
How can we limit global warming?
Limiting the rising in global warming is theoretically achievable, but politically, socially, and economically difficult.
Those same sources of greenhouse gas emissions must be limited to reduce warming. For example, oil and gas used to generate electricity or power industrial manufacturing will need to be replaced by net zero emission technology like wind and solar power. Transportation, another major source of emissions, will need to integrate more electric vehicles, public transportation, and innovative urban design, such as safe bike lanes and walkable cities.
( Learn more about solutions to limit global warming. )
One global warming solution that was once considered far fetched is now being taken more seriously: geoengineering. This type of technology relies on manipulating the Earth's atmosphere to physically block the warming rays of the sun or by sucking carbon dioxide straight out of the sky.
Restoring nature may also help limit warming. Trees, oceans, wetlands, and other ecosystems help absorb excess carbon—but when they're lost, so too is their potential to fight climate change.
Ultimately, we'll need to adapt to warming temperatures, building homes to withstand sea level rise for example, or more efficiently cooling homes during heat waves.
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January 10, 2014
How the "Global Cooling" Story Came to Be
By Doug Struck & The Daily Climate
BOSTON – Temperatures have plunged to record lows on the East Coast, and once again Peter Gwynne is being heralded as a journalist ahead of his time. By some.
Gwynne was the science editor of Newsweek 39 years ago when he pulled together some interviews from scientists and wrote a nine-paragraph story about how the planet was getting cooler.
Ever since, Gwynne's "global cooling" story – and a similar Time Magazine piece – have been brandished gleefully by those who say it shows global warming is not happening, or at least that scientists – and often journalists – don't know what they are talking about.
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Fox News loves to cite it. So does Rush Limbaugh. Sen. James Inhofe, R-Okla., has quoted the story on the Senate floor.
Gwynne, now 72, is a bit chagrinned that from a long career of distinguished science and technology reporting, he is most remembered for this one story.
"I have, in fact, won prizes for science writing," he said, with just a whiff of annoyance, in an interview this week.
His April 28, 1975 piece has been used by Forbes as evidence of what the magazine called "The Fiction of Climate Science." It has been set to music on a YouTube video. It has popped up in a slew of finger-wagging blogs and websites dedicated to everything from climate denial to one puzzling circuit of logic entitled "Impeach Obama, McCain and Boehner Today."
From the latest crop:
Lou Dobbs on Fox News: "This cycle of science… if we go back to 1970, the fear then was global cooling. "
Rush Limbaugh: "I call [global warming] a hoax… A 1975 Newsweek cover was gonna talk about the ice age coming. So they're really confused how to play it."
Sean Hannity on Fox News: "If you go back to Time Magazine, they actually were proclaiming the next ice age is coming, now it's become global warming… How do you believe the same people that were predicting just a couple decades ago that the new ice age is coming?"
Donald J. Trump: "This very expensive global warming bullshit has got to stop. Our planet is freezing.…"
Most of the time, Gwynne, who still writes on technology and science from his home in Cape Cod, Mass., takes it good-naturedly.
"It's part of the game, once you get from science to politics, that's the way it's played," he said. "I just hope people don't think I think that way."
And still, Gwynne notes of his story, "I stand by it. It was accurate at the time."
The story observed – accurately – that there had been a gradual decrease in global average temperatures from about 1940, now believed to be a consequence of soot and aerosols that offered a partial shield to the earth as well as the gradual retreat of an abnormally warm interlude.
Some climatologists predicted the trend would continue, inching the earth toward the colder averages of the "Little Ice Age" from the 16th to 19th centuries.
"When I wrote this story I did not see it as a blockbuster," Gwynne recalled. "It was just an intriguing piece about what a certain group in a certain niche of climatology was thinking."
And, revisionist lore aside, it was hardly a cover story. It was a one-page article on page 64. It was, Gwynne concedes, written with a bit of over-ventilated style that sometimes marked the magazine's prose: "There are ominous signs the earth's weather patterns have begun to change dramatically..." the piece begins, and warns of a possible "dramatic decline in food production."
"Newsweek being Newsweek, we might have pushed the envelope a little bit more than I would have wanted," Gwynne offered.
But the story was tantalizing enough that other variations – somewhat more nuanced – were written by the New York Times and National Geographic, among others. The theory picked up support from some pretty reputable scientists: the late, esteemed Stephen Schneider of Stanford endorsed a book on the issue.
But there also was a small but growing counter-theory that carbon dioxide and other pollutants accompanying the Industrial Age were creating a warming belt in the atmosphere, and by about 1980 it was clear that the earth's average temperature was headed upward.
Even today, "there is some degree of uncertainty about natural variability," acknowledged Mark McCaffrey, programs and policy director of the National Center for Science Education based in Oakland, Calif. "If it weren't for the fact that humans had become a force of nature, we would be slipping back into an ice age, according to orbital cycles."
But earth's glacial rhythms are "being overridden by human activities, especially burning fossil fuels," McCaffrey noted. The stories about global cooling "are convenient for people to trot out and wave around," he said, but they miss the point:
"What's clear is we are a force of nature. Human activity – the burning of fossil fuels and land change – is having a massive influence. We are in the midst of this giant geoengineering experiment."
And, Gwynne protested: "I wrote this in 1975!"
Born in England, Gwynne has written for a slew of American and foreign outlets. He left Newsweek in 1981, he ran Technology Review at the Massachusetts Institute of Technology, covered space for High Technology , worked for The Scientist in Washington, moved to Hong Kong to run Asia Technology for Dow Jones, and returned to the United States to freelance in 1994.
He remains the North American correspondent for Physics World, based in England, from which perspective he views the "weird and wonderful" American relationship with science. "It's been American science and scientists – particularly NASA – that showed the climate is changing," he noted. Yet, unlike in most of Europe, American politicians remain divided over climate science.
The unsavory afterlife of his 1975 story clearly has not soured his journalistic fervor. "I've been able to write for a lot of different audiences, physicists, engineers and the general public," Gwynne said. "I've been willing to accept that some of that is misused and misinterpreted."
By and large, he added, the U.S. science press has done "a pretty good job" of covering climate change. But "the political press doesn't check. It tends to do 'on the one hand, on the other hand.' A lot of reporters simply will not go into issues like global warming with any understanding that the sides are not equal."
Journalists should not ignore climate deniers, he cautioned. "You have to give all sides a fair hearing." But that does not mean they have to be treated equally "if they don't have the data." To do so, he said, is false balance "that leaves readers out on a limb."
"Your job as a journalist is to give each side its best shot," said Gwynne. Even if the ammunition is four decades old.
This article originally appeared at The Daily Climate , the climate change news source published by Environmental Health Sciences, a non-profit media company.
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- 28 February 2022
Climate change is hitting the planet faster than scientists originally thought
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The negative impacts of climate change are mounting much faster than scientists predicted less than a decade ago, according to the latest report from a United Nations climate panel . Many impacts are unavoidable and will hit the world’s most vulnerable populations hardest, it warns — but collective action from governments to both curb greenhouse-gas emissions and prepare communities to live with global warming could yet avert the worst outcomes.
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The Science of Climate Change Explained: Facts, Evidence and Proof
Definitive answers to the big questions.
Credit... Photo Illustration by Andrea D'Aquino
By Julia Rosen
Ms. Rosen is a journalist with a Ph.D. in geology. Her research involved studying ice cores from Greenland and Antarctica to understand past climate changes.
- Published April 19, 2021 Updated Nov. 6, 2021
The science of climate change is more solid and widely agreed upon than you might think. But the scope of the topic, as well as rampant disinformation, can make it hard to separate fact from fiction. Here, we’ve done our best to present you with not only the most accurate scientific information, but also an explanation of how we know it.
How do we know climate change is really happening?
How much agreement is there among scientists about climate change, do we really only have 150 years of climate data how is that enough to tell us about centuries of change, how do we know climate change is caused by humans, since greenhouse gases occur naturally, how do we know they’re causing earth’s temperature to rise, why should we be worried that the planet has warmed 2°f since the 1800s, is climate change a part of the planet’s natural warming and cooling cycles, how do we know global warming is not because of the sun or volcanoes, how can winters and certain places be getting colder if the planet is warming, wildfires and bad weather have always happened. how do we know there’s a connection to climate change, how bad are the effects of climate change going to be, what will it cost to do something about climate change, versus doing nothing.
Climate change is often cast as a prediction made by complicated computer models. But the scientific basis for climate change is much broader, and models are actually only one part of it (and, for what it’s worth, they’re surprisingly accurate ).
For more than a century , scientists have understood the basic physics behind why greenhouse gases like carbon dioxide cause warming. These gases make up just a small fraction of the atmosphere but exert outsized control on Earth’s climate by trapping some of the planet’s heat before it escapes into space. This greenhouse effect is important: It’s why a planet so far from the sun has liquid water and life!
However, during the Industrial Revolution, people started burning coal and other fossil fuels to power factories, smelters and steam engines, which added more greenhouse gases to the atmosphere. Ever since, human activities have been heating the planet.
We know this is true thanks to an overwhelming body of evidence that begins with temperature measurements taken at weather stations and on ships starting in the mid-1800s. Later, scientists began tracking surface temperatures with satellites and looking for clues about climate change in geologic records. Together, these data all tell the same story: Earth is getting hotter.
Average global temperatures have increased by 2.2 degrees Fahrenheit, or 1.2 degrees Celsius, since 1880, with the greatest changes happening in the late 20th century. Land areas have warmed more than the sea surface and the Arctic has warmed the most — by more than 4 degrees Fahrenheit just since the 1960s. Temperature extremes have also shifted. In the United States, daily record highs now outnumber record lows two-to-one.
Where it was cooler or warmer in 2020 compared with the middle of the 20th century
This warming is unprecedented in recent geologic history. A famous illustration, first published in 1998 and often called the hockey-stick graph, shows how temperatures remained fairly flat for centuries (the shaft of the stick) before turning sharply upward (the blade). It’s based on data from tree rings, ice cores and other natural indicators. And the basic picture , which has withstood decades of scrutiny from climate scientists and contrarians alike, shows that Earth is hotter today than it’s been in at least 1,000 years, and probably much longer.
In fact, surface temperatures actually mask the true scale of climate change, because the ocean has absorbed 90 percent of the heat trapped by greenhouse gases . Measurements collected over the last six decades by oceanographic expeditions and networks of floating instruments show that every layer of the ocean is warming up. According to one study , the ocean has absorbed as much heat between 1997 and 2015 as it did in the previous 130 years.
We also know that climate change is happening because we see the effects everywhere. Ice sheets and glaciers are shrinking while sea levels are rising. Arctic sea ice is disappearing. In the spring, snow melts sooner and plants flower earlier. Animals are moving to higher elevations and latitudes to find cooler conditions. And droughts, floods and wildfires have all gotten more extreme. Models predicted many of these changes, but observations show they are now coming to pass.
Back to top .
There’s no denying that scientists love a good, old-fashioned argument. But when it comes to climate change, there is virtually no debate: Numerous studies have found that more than 90 percent of scientists who study Earth’s climate agree that the planet is warming and that humans are the primary cause. Most major scientific bodies, from NASA to the World Meteorological Organization , endorse this view. That’s an astounding level of consensus given the contrarian, competitive nature of the scientific enterprise, where questions like what killed the dinosaurs remain bitterly contested .
Scientific agreement about climate change started to emerge in the late 1980s, when the influence of human-caused warming began to rise above natural climate variability. By 1991, two-thirds of earth and atmospheric scientists surveyed for an early consensus study said that they accepted the idea of anthropogenic global warming. And by 1995, the Intergovernmental Panel on Climate Change, a famously conservative body that periodically takes stock of the state of scientific knowledge, concluded that “the balance of evidence suggests that there is a discernible human influence on global climate.” Currently, more than 97 percent of publishing climate scientists agree on the existence and cause of climate change (as does nearly 60 percent of the general population of the United States).
So where did we get the idea that there’s still debate about climate change? A lot of it came from coordinated messaging campaigns by companies and politicians that opposed climate action. Many pushed the narrative that scientists still hadn’t made up their minds about climate change, even though that was misleading. Frank Luntz, a Republican consultant, explained the rationale in an infamous 2002 memo to conservative lawmakers: “Should the public come to believe that the scientific issues are settled, their views about global warming will change accordingly,” he wrote. Questioning consensus remains a common talking point today, and the 97 percent figure has become something of a lightning rod .
To bolster the falsehood of lingering scientific doubt, some people have pointed to things like the Global Warming Petition Project, which urged the United States government to reject the Kyoto Protocol of 1997, an early international climate agreement. The petition proclaimed that climate change wasn’t happening, and even if it were, it wouldn’t be bad for humanity. Since 1998, more than 30,000 people with science degrees have signed it. However, nearly 90 percent of them studied something other than Earth, atmospheric or environmental science, and the signatories included just 39 climatologists. Most were engineers, doctors, and others whose training had little to do with the physics of the climate system.
A few well-known researchers remain opposed to the scientific consensus. Some, like Willie Soon, a researcher affiliated with the Harvard-Smithsonian Center for Astrophysics, have ties to the fossil fuel industry . Others do not, but their assertions have not held up under the weight of evidence. At least one prominent skeptic, the physicist Richard Muller, changed his mind after reassessing historical temperature data as part of the Berkeley Earth project. His team’s findings essentially confirmed the results he had set out to investigate, and he came away firmly convinced that human activities were warming the planet. “Call me a converted skeptic,” he wrote in an Op-Ed for the Times in 2012.
Mr. Luntz, the Republican pollster, has also reversed his position on climate change and now advises politicians on how to motivate climate action.
A final note on uncertainty: Denialists often use it as evidence that climate science isn’t settled. However, in science, uncertainty doesn’t imply a lack of knowledge. Rather, it’s a measure of how well something is known. In the case of climate change, scientists have found a range of possible future changes in temperature, precipitation and other important variables — which will depend largely on how quickly we reduce emissions. But uncertainty does not undermine their confidence that climate change is real and that people are causing it.
Earth’s climate is inherently variable. Some years are hot and others are cold, some decades bring more hurricanes than others, some ancient droughts spanned the better part of centuries. Glacial cycles operate over many millenniums. So how can scientists look at data collected over a relatively short period of time and conclude that humans are warming the planet? The answer is that the instrumental temperature data that we have tells us a lot, but it’s not all we have to go on.
Historical records stretch back to the 1880s (and often before), when people began to regularly measure temperatures at weather stations and on ships as they traversed the world’s oceans. These data show a clear warming trend during the 20th century.
Global average temperature compared with the middle of the 20th century
Some have questioned whether these records could be skewed, for instance, by the fact that a disproportionate number of weather stations are near cities, which tend to be hotter than surrounding areas as a result of the so-called urban heat island effect. However, researchers regularly correct for these potential biases when reconstructing global temperatures. In addition, warming is corroborated by independent data like satellite observations, which cover the whole planet, and other ways of measuring temperature changes.
Much has also been made of the small dips and pauses that punctuate the rising temperature trend of the last 150 years. But these are just the result of natural climate variability or other human activities that temporarily counteract greenhouse warming. For instance, in the mid-1900s, internal climate dynamics and light-blocking pollution from coal-fired power plants halted global warming for a few decades. (Eventually, rising greenhouse gases and pollution-control laws caused the planet to start heating up again.) Likewise, the so-called warming hiatus of the 2000s was partly a result of natural climate variability that allowed more heat to enter the ocean rather than warm the atmosphere. The years since have been the hottest on record .
Still, could the entire 20th century just be one big natural climate wiggle? To address that question, we can look at other kinds of data that give a longer perspective. Researchers have used geologic records like tree rings, ice cores, corals and sediments that preserve information about prehistoric climates to extend the climate record. The resulting picture of global temperature change is basically flat for centuries, then turns sharply upward over the last 150 years. It has been a target of climate denialists for decades. However, study after study has confirmed the results , which show that the planet hasn’t been this hot in at least 1,000 years, and probably longer.
Scientists have studied past climate changes to understand the factors that can cause the planet to warm or cool. The big ones are changes in solar energy, ocean circulation, volcanic activity and the amount of greenhouse gases in the atmosphere. And they have each played a role at times.
For example, 300 years ago, a combination of reduced solar output and increased volcanic activity cooled parts of the planet enough that Londoners regularly ice skated on the Thames . About 12,000 years ago, major changes in Atlantic circulation plunged the Northern Hemisphere into a frigid state. And 56 million years ago, a giant burst of greenhouse gases, from volcanic activity or vast deposits of methane (or both), abruptly warmed the planet by at least 9 degrees Fahrenheit, scrambling the climate, choking the oceans and triggering mass extinctions.
In trying to determine the cause of current climate changes, scientists have looked at all of these factors . The first three have varied a bit over the last few centuries and they have quite likely had modest effects on climate , particularly before 1950. But they cannot account for the planet’s rapidly rising temperature, especially in the second half of the 20th century, when solar output actually declined and volcanic eruptions exerted a cooling effect.
That warming is best explained by rising greenhouse gas concentrations . Greenhouse gases have a powerful effect on climate (see the next question for why). And since the Industrial Revolution, humans have been adding more of them to the atmosphere, primarily by extracting and burning fossil fuels like coal, oil and gas, which releases carbon dioxide.
Bubbles of ancient air trapped in ice show that, before about 1750, the concentration of carbon dioxide in the atmosphere was roughly 280 parts per million. It began to rise slowly and crossed the 300 p.p.m. threshold around 1900. CO2 levels then accelerated as cars and electricity became big parts of modern life, recently topping 420 p.p.m . The concentration of methane, the second most important greenhouse gas, has more than doubled. We’re now emitting carbon much faster than it was released 56 million years ago .
30 billion metric tons
Carbon dioxide emitted worldwide 1850-2017
Rest of world
E.U. and U.K.
These rapid increases in greenhouse gases have caused the climate to warm abruptly. In fact, climate models suggest that greenhouse warming can explain virtually all of the temperature change since 1950. According to the most recent report by the Intergovernmental Panel on Climate Change, which assesses published scientific literature, natural drivers and internal climate variability can only explain a small fraction of late-20th century warming.
Another study put it this way: The odds of current warming occurring without anthropogenic greenhouse gas emissions are less than 1 in 100,000 .
But greenhouse gases aren’t the only climate-altering compounds people put into the air. Burning fossil fuels also produces particulate pollution that reflects sunlight and cools the planet. Scientists estimate that this pollution has masked up to half of the greenhouse warming we would have otherwise experienced.
Greenhouse gases like water vapor and carbon dioxide serve an important role in the climate. Without them, Earth would be far too cold to maintain liquid water and humans would not exist!
Here’s how it works: the planet’s temperature is basically a function of the energy the Earth absorbs from the sun (which heats it up) and the energy Earth emits to space as infrared radiation (which cools it down). Because of their molecular structure, greenhouse gases temporarily absorb some of that outgoing infrared radiation and then re-emit it in all directions, sending some of that energy back toward the surface and heating the planet . Scientists have understood this process since the 1850s .
Greenhouse gas concentrations have varied naturally in the past. Over millions of years, atmospheric CO2 levels have changed depending on how much of the gas volcanoes belched into the air and how much got removed through geologic processes. On time scales of hundreds to thousands of years, concentrations have changed as carbon has cycled between the ocean, soil and air.
Today, however, we are the ones causing CO2 levels to increase at an unprecedented pace by taking ancient carbon from geologic deposits of fossil fuels and putting it into the atmosphere when we burn them. Since 1750, carbon dioxide concentrations have increased by almost 50 percent. Methane and nitrous oxide, other important anthropogenic greenhouse gases that are released mainly by agricultural activities, have also spiked over the last 250 years.
We know based on the physics described above that this should cause the climate to warm. We also see certain telltale “fingerprints” of greenhouse warming. For example, nights are warming even faster than days because greenhouse gases don’t go away when the sun sets. And upper layers of the atmosphere have actually cooled, because more energy is being trapped by greenhouse gases in the lower atmosphere.
We also know that we are the cause of rising greenhouse gas concentrations — and not just because we can measure the CO2 coming out of tailpipes and smokestacks. We can see it in the chemical signature of the carbon in CO2.
Carbon comes in three different masses: 12, 13 and 14. Things made of organic matter (including fossil fuels) tend to have relatively less carbon-13. Volcanoes tend to produce CO2 with relatively more carbon-13. And over the last century, the carbon in atmospheric CO2 has gotten lighter, pointing to an organic source.
We can tell it’s old organic matter by looking for carbon-14, which is radioactive and decays over time. Fossil fuels are too ancient to have any carbon-14 left in them, so if they were behind rising CO2 levels, you would expect the amount of carbon-14 in the atmosphere to drop, which is exactly what the data show .
It’s important to note that water vapor is the most abundant greenhouse gas in the atmosphere. However, it does not cause warming; instead it responds to it . That’s because warmer air holds more moisture, which creates a snowball effect in which human-caused warming allows the atmosphere to hold more water vapor and further amplifies climate change. This so-called feedback cycle has doubled the warming caused by anthropogenic greenhouse gas emissions.
A common source of confusion when it comes to climate change is the difference between weather and climate. Weather is the constantly changing set of meteorological conditions that we experience when we step outside, whereas climate is the long-term average of those conditions, usually calculated over a 30-year period. Or, as some say: Weather is your mood and climate is your personality.
So while 2 degrees Fahrenheit doesn’t represent a big change in the weather, it’s a huge change in climate. As we’ve already seen, it’s enough to melt ice and raise sea levels, to shift rainfall patterns around the world and to reorganize ecosystems, sending animals scurrying toward cooler habitats and killing trees by the millions.
It’s also important to remember that two degrees represents the global average, and many parts of the world have already warmed by more than that. For example, land areas have warmed about twice as much as the sea surface. And the Arctic has warmed by about 5 degrees. That’s because the loss of snow and ice at high latitudes allows the ground to absorb more energy, causing additional heating on top of greenhouse warming.
Relatively small long-term changes in climate averages also shift extremes in significant ways. For instance, heat waves have always happened, but they have shattered records in recent years. In June of 2020, a town in Siberia registered temperatures of 100 degrees . And in Australia, meteorologists have added a new color to their weather maps to show areas where temperatures exceed 125 degrees. Rising sea levels have also increased the risk of flooding because of storm surges and high tides. These are the foreshocks of climate change.
And we are in for more changes in the future — up to 9 degrees Fahrenheit of average global warming by the end of the century, in the worst-case scenario . For reference, the difference in global average temperatures between now and the peak of the last ice age, when ice sheets covered large parts of North America and Europe, is about 11 degrees Fahrenheit.
Under the Paris Climate Agreement, which President Biden recently rejoined, countries have agreed to try to limit total warming to between 1.5 and 2 degrees Celsius, or 2.7 and 3.6 degrees Fahrenheit, since preindustrial times. And even this narrow range has huge implications . According to scientific studies, the difference between 2.7 and 3.6 degrees Fahrenheit will very likely mean the difference between coral reefs hanging on or going extinct, and between summer sea ice persisting in the Arctic or disappearing completely. It will also determine how many millions of people suffer from water scarcity and crop failures, and how many are driven from their homes by rising seas. In other words, one degree Fahrenheit makes a world of difference.
Earth’s climate has always changed. Hundreds of millions of years ago, the entire planet froze . Fifty million years ago, alligators lived in what we now call the Arctic . And for the last 2.6 million years, the planet has cycled between ice ages when the planet was up to 11 degrees cooler and ice sheets covered much of North America and Europe, and milder interglacial periods like the one we’re in now.
Climate denialists often point to these natural climate changes as a way to cast doubt on the idea that humans are causing climate to change today. However, that argument rests on a logical fallacy. It’s like “seeing a murdered body and concluding that people have died of natural causes in the past, so the murder victim must also have died of natural causes,” a team of social scientists wrote in The Debunking Handbook , which explains the misinformation strategies behind many climate myths.
Indeed, we know that different mechanisms caused the climate to change in the past. Glacial cycles, for example, were triggered by periodic variations in Earth’s orbit , which take place over tens of thousands of years and change how solar energy gets distributed around the globe and across the seasons.
These orbital variations don’t affect the planet’s temperature much on their own. But they set off a cascade of other changes in the climate system; for instance, growing or melting vast Northern Hemisphere ice sheets and altering ocean circulation. These changes, in turn, affect climate by altering the amount of snow and ice, which reflect sunlight, and by changing greenhouse gas concentrations. This is actually part of how we know that greenhouse gases have the ability to significantly affect Earth’s temperature.
For at least the last 800,000 years , atmospheric CO2 concentrations oscillated between about 180 parts per million during ice ages and about 280 p.p.m. during warmer periods, as carbon moved between oceans, forests, soils and the atmosphere. These changes occurred in lock step with global temperatures, and are a major reason the entire planet warmed and cooled during glacial cycles, not just the frozen poles.
Today, however, CO2 levels have soared to 420 p.p.m. — the highest they’ve been in at least three million years . The concentration of CO2 is also increasing about 100 times faster than it did at the end of the last ice age. This suggests something else is going on, and we know what it is: Since the Industrial Revolution, humans have been burning fossil fuels and releasing greenhouse gases that are heating the planet now (see Question 5 for more details on how we know this, and Questions 4 and 8 for how we know that other natural forces aren’t to blame).
Over the next century or two, societies and ecosystems will experience the consequences of this climate change. But our emissions will have even more lasting geologic impacts: According to some studies, greenhouse gas levels may have already warmed the planet enough to delay the onset of the next glacial cycle for at least an additional 50,000 years.
The sun is the ultimate source of energy in Earth’s climate system, so it’s a natural candidate for causing climate change. And solar activity has certainly changed over time. We know from satellite measurements and other astronomical observations that the sun’s output changes on 11-year cycles. Geologic records and sunspot numbers, which astronomers have tracked for centuries, also show long-term variations in the sun’s activity, including some exceptionally quiet periods in the late 1600s and early 1800s.
We know that, from 1900 until the 1950s, solar irradiance increased. And studies suggest that this had a modest effect on early 20th century climate, explaining up to 10 percent of the warming that’s occurred since the late 1800s. However, in the second half of the century, when the most warming occurred, solar activity actually declined . This disparity is one of the main reasons we know that the sun is not the driving force behind climate change.
Another reason we know that solar activity hasn’t caused recent warming is that, if it had, all the layers of the atmosphere should be heating up. Instead, data show that the upper atmosphere has actually cooled in recent decades — a hallmark of greenhouse warming .
So how about volcanoes? Eruptions cool the planet by injecting ash and aerosol particles into the atmosphere that reflect sunlight. We’ve observed this effect in the years following large eruptions. There are also some notable historical examples, like when Iceland’s Laki volcano erupted in 1783, causing widespread crop failures in Europe and beyond, and the “ year without a summer ,” which followed the 1815 eruption of Mount Tambora in Indonesia.
Since volcanoes mainly act as climate coolers, they can’t really explain recent warming. However, scientists say that they may also have contributed slightly to rising temperatures in the early 20th century. That’s because there were several large eruptions in the late 1800s that cooled the planet, followed by a few decades with no major volcanic events when warming caught up. During the second half of the 20th century, though, several big eruptions occurred as the planet was heating up fast. If anything, they temporarily masked some amount of human-caused warming.
The second way volcanoes can impact climate is by emitting carbon dioxide. This is important on time scales of millions of years — it’s what keeps the planet habitable (see Question 5 for more on the greenhouse effect). But by comparison to modern anthropogenic emissions, even big eruptions like Krakatoa and Mount St. Helens are just a drop in the bucket. After all, they last only a few hours or days, while we burn fossil fuels 24-7. Studies suggest that, today, volcanoes account for 1 to 2 percent of total CO2 emissions.
When a big snowstorm hits the United States, climate denialists can try to cite it as proof that climate change isn’t happening. In 2015, Senator James Inhofe, an Oklahoma Republican, famously lobbed a snowball in the Senate as he denounced climate science. But these events don’t actually disprove climate change.
While there have been some memorable storms in recent years, winters are actually warming across the world. In the United States, average temperatures in December, January and February have increased by about 2.5 degrees this century.
On the flip side, record cold days are becoming less common than record warm days. In the United States, record highs now outnumber record lows two-to-one . And ever-smaller areas of the country experience extremely cold winter temperatures . (The same trends are happening globally.)
So what’s with the blizzards? Weather always varies, so it’s no surprise that we still have severe winter storms even as average temperatures rise. However, some studies suggest that climate change may be to blame. One possibility is that rapid Arctic warming has affected atmospheric circulation, including the fast-flowing, high-altitude air that usually swirls over the North Pole (a.k.a. the Polar Vortex ). Some studies suggest that these changes are bringing more frigid temperatures to lower latitudes and causing weather systems to stall , allowing storms to produce more snowfall. This may explain what we’ve experienced in the U.S. over the past few decades, as well as a wintertime cooling trend in Siberia , although exactly how the Arctic affects global weather remains a topic of ongoing scientific debate .
Climate change may also explain the apparent paradox behind some of the other places on Earth that haven’t warmed much. For instance, a splotch of water in the North Atlantic has cooled in recent years, and scientists say they suspect that may be because ocean circulation is slowing as a result of freshwater streaming off a melting Greenland . If this circulation grinds almost to a halt, as it’s done in the geologic past, it would alter weather patterns around the world.
Not all cold weather stems from some counterintuitive consequence of climate change. But it’s a good reminder that Earth’s climate system is complex and chaotic, so the effects of human-caused changes will play out differently in different places. That’s why “global warming” is a bit of an oversimplification. Instead, some scientists have suggested that the phenomenon of human-caused climate change would more aptly be called “ global weirding .”
Extreme weather and natural disasters are part of life on Earth — just ask the dinosaurs. But there is good evidence that climate change has increased the frequency and severity of certain phenomena like heat waves, droughts and floods. Recent research has also allowed scientists to identify the influence of climate change on specific events.
Let’s start with heat waves . Studies show that stretches of abnormally high temperatures now happen about five times more often than they would without climate change, and they last longer, too. Climate models project that, by the 2040s, heat waves will be about 12 times more frequent. And that’s concerning since extreme heat often causes increased hospitalizations and deaths, particularly among older people and those with underlying health conditions. In the summer of 2003, for example, a heat wave caused an estimated 70,000 excess deaths across Europe. (Human-caused warming amplified the death toll .)
Climate change has also exacerbated droughts , primarily by increasing evaporation. Droughts occur naturally because of random climate variability and factors like whether El Niño or La Niña conditions prevail in the tropical Pacific. But some researchers have found evidence that greenhouse warming has been affecting droughts since even before the Dust Bowl . And it continues to do so today. According to one analysis , the drought that afflicted the American Southwest from 2000 to 2018 was almost 50 percent more severe because of climate change. It was the worst drought the region had experienced in more than 1,000 years.
Rising temperatures have also increased the intensity of heavy precipitation events and the flooding that often follows. For example, studies have found that, because warmer air holds more moisture, Hurricane Harvey, which struck Houston in 2017, dropped between 15 and 40 percent more rainfall than it would have without climate change.
It’s still unclear whether climate change is changing the overall frequency of hurricanes, but it is making them stronger . And warming appears to favor certain kinds of weather patterns, like the “ Midwest Water Hose ” events that caused devastating flooding across the Midwest in 2019 .
It’s important to remember that in most natural disasters, there are multiple factors at play. For instance, the 2019 Midwest floods occurred after a recent cold snap had frozen the ground solid, preventing the soil from absorbing rainwater and increasing runoff into the Missouri and Mississippi Rivers. These waterways have also been reshaped by levees and other forms of river engineering, some of which failed in the floods.
Wildfires are another phenomenon with multiple causes. In many places, fire risk has increased because humans have aggressively fought natural fires and prevented Indigenous peoples from carrying out traditional burning practices. This has allowed fuel to accumulate that makes current fires worse .
However, climate change still plays a major role by heating and drying forests, turning them into tinderboxes. Studies show that warming is the driving factor behind the recent increases in wildfires; one analysis found that climate change is responsible for doubling the area burned across the American West between 1984 and 2015. And researchers say that warming will only make fires bigger and more dangerous in the future.
It depends on how aggressively we act to address climate change. If we continue with business as usual, by the end of the century, it will be too hot to go outside during heat waves in the Middle East and South Asia . Droughts will grip Central America, the Mediterranean and southern Africa. And many island nations and low-lying areas, from Texas to Bangladesh, will be overtaken by rising seas. Conversely, climate change could bring welcome warming and extended growing seasons to the upper Midwest , Canada, the Nordic countries and Russia . Farther north, however, the loss of snow, ice and permafrost will upend the traditions of Indigenous peoples and threaten infrastructure.
It’s complicated, but the underlying message is simple: unchecked climate change will likely exacerbate existing inequalities . At a national level, poorer countries will be hit hardest, even though they have historically emitted only a fraction of the greenhouse gases that cause warming. That’s because many less developed countries tend to be in tropical regions where additional warming will make the climate increasingly intolerable for humans and crops. These nations also often have greater vulnerabilities, like large coastal populations and people living in improvised housing that is easily damaged in storms. And they have fewer resources to adapt, which will require expensive measures like redesigning cities, engineering coastlines and changing how people grow food.
Already, between 1961 and 2000, climate change appears to have harmed the economies of the poorest countries while boosting the fortunes of the wealthiest nations that have done the most to cause the problem, making the global wealth gap 25 percent bigger than it would otherwise have been. Similarly, the Global Climate Risk Index found that lower income countries — like Myanmar, Haiti and Nepal — rank high on the list of nations most affected by extreme weather between 1999 and 2018. Climate change has also contributed to increased human migration, which is expected to increase significantly .
Even within wealthy countries, the poor and marginalized will suffer the most. People with more resources have greater buffers, like air-conditioners to keep their houses cool during dangerous heat waves, and the means to pay the resulting energy bills. They also have an easier time evacuating their homes before disasters, and recovering afterward. Lower income people have fewer of these advantages, and they are also more likely to live in hotter neighborhoods and work outdoors, where they face the brunt of climate change.
These inequalities will play out on an individual, community, and regional level. A 2017 analysis of the U.S. found that, under business as usual, the poorest one-third of counties, which are concentrated in the South, will experience damages totaling as much as 20 percent of gross domestic product, while others, mostly in the northern part of the country, will see modest economic gains. Solomon Hsiang, an economist at University of California, Berkeley, and the lead author of the study, has said that climate change “may result in the largest transfer of wealth from the poor to the rich in the country’s history.”
Even the climate “winners” will not be immune from all climate impacts, though. Desirable locations will face an influx of migrants. And as the coronavirus pandemic has demonstrated, disasters in one place quickly ripple across our globalized economy. For instance, scientists expect climate change to increase the odds of multiple crop failures occurring at the same time in different places, throwing the world into a food crisis .
On top of that, warmer weather is aiding the spread of infectious diseases and the vectors that transmit them, like ticks and mosquitoes . Research has also identified troubling correlations between rising temperatures and increased interpersonal violence , and climate change is widely recognized as a “threat multiplier” that increases the odds of larger conflicts within and between countries. In other words, climate change will bring many changes that no amount of money can stop. What could help is taking action to limit warming.
One of the most common arguments against taking aggressive action to combat climate change is that doing so will kill jobs and cripple the economy. But this implies that there’s an alternative in which we pay nothing for climate change. And unfortunately, there isn’t. In reality, not tackling climate change will cost a lot , and cause enormous human suffering and ecological damage, while transitioning to a greener economy would benefit many people and ecosystems around the world.
Let’s start with how much it will cost to address climate change. To keep warming well below 2 degrees Celsius, the goal of the Paris Climate Agreement, society will have to reach net zero greenhouse gas emissions by the middle of this century. That will require significant investments in things like renewable energy, electric cars and charging infrastructure, not to mention efforts to adapt to hotter temperatures, rising sea-levels and other unavoidable effects of current climate changes. And we’ll have to make changes fast.
Estimates of the cost vary widely. One recent study found that keeping warming to 2 degrees Celsius would require a total investment of between $4 trillion and $60 trillion, with a median estimate of $16 trillion, while keeping warming to 1.5 degrees Celsius could cost between $10 trillion and $100 trillion, with a median estimate of $30 trillion. (For reference, the entire world economy was about $88 trillion in 2019.) Other studies have found that reaching net zero will require annual investments ranging from less than 1.5 percent of global gross domestic product to as much as 4 percent . That’s a lot, but within the range of historical energy investments in countries like the U.S.
Now, let’s consider the costs of unchecked climate change, which will fall hardest on the most vulnerable. These include damage to property and infrastructure from sea-level rise and extreme weather, death and sickness linked to natural disasters, pollution and infectious disease, reduced agricultural yields and lost labor productivity because of rising temperatures, decreased water availability and increased energy costs, and species extinction and habitat destruction. Dr. Hsiang, the U.C. Berkeley economist, describes it as “death by a thousand cuts.”
As a result, climate damages are hard to quantify. Moody’s Analytics estimates that even 2 degrees Celsius of warming will cost the world $69 trillion by 2100, and economists expect the toll to keep rising with the temperature. In a recent survey , economists estimated the cost would equal 5 percent of global G.D.P. at 3 degrees Celsius of warming (our trajectory under current policies) and 10 percent for 5 degrees Celsius. Other research indicates that, if current warming trends continue, global G.D.P. per capita will decrease between 7 percent and 23 percent by the end of the century — an economic blow equivalent to multiple coronavirus pandemics every year. And some fear these are vast underestimates .
Already, studies suggest that climate change has slashed incomes in the poorest countries by as much as 30 percent and reduced global agricultural productivity by 21 percent since 1961. Extreme weather events have also racked up a large bill. In 2020, in the United States alone, climate-related disasters like hurricanes, droughts, and wildfires caused nearly $100 billion in damages to businesses, property and infrastructure, compared to an average of $18 billion per year in the 1980s.
Given the steep price of inaction, many economists say that addressing climate change is a better deal . It’s like that old saying: an ounce of prevention is worth a pound of cure. In this case, limiting warming will greatly reduce future damage and inequality caused by climate change. It will also produce so-called co-benefits, like saving one million lives every year by reducing air pollution, and millions more from eating healthier, climate-friendly diets. Some studies even find that meeting the Paris Agreement goals could create jobs and increase global G.D.P . And, of course, reining in climate change will spare many species and ecosystems upon which humans depend — and which many people believe to have their own innate value.
The challenge is that we need to reduce emissions now to avoid damages later, which requires big investments over the next few decades. And the longer we delay, the more we will pay to meet the Paris goals. One recent analysis found that reaching net-zero by 2050 would cost the U.S. almost twice as much if we waited until 2030 instead of acting now. But even if we miss the Paris target, the economics still make a strong case for climate action, because every additional degree of warming will cost us more — in dollars, and in lives.
Veronica Penney contributed reporting.
Illustration photographs by Esther Horvath, Max Whittaker, David Maurice Smith and Talia Herman for The New York Times; Esther Horvath/Alfred-Wegener-Institut
An earlier version of this article misidentified the authors of The Debunking Handbook. It was written by social scientists who study climate communication, not a team of climate scientists.
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Write an article on Global warming in about 200 words
- Article Writing
Global warming or climate change has today become a major threat to the mankind. The Earth’s temperature is on the rise and there are various reasons for it such as greenhouse gases emanating from carbon dioxide ($CO_2$) emissions, burning of fossil fuels or deforestation.
Impact of Greenhouse Gases
The rise in the levels of carbon dioxide ($CO_2$) leads to substantial increase in temperature. It is because $CO_2$ remains concentrated in the atmosphere for even hundreds of years. Due to activities like fossil fuel combustion for electricity generation, transportation, and heating, human beings have contributed to increase in the $CO_2$ concentration in the atmosphere.
Global Warming: A Gradual Phenomenon
Recent years have been unusually warm, causing worldwide concern. But the fact is that the increase in carbon dioxide actually began in 1800, due to the deforestation of a large chunk of North-eastern American, besides forested parts of the world. The things became worse with emissions in the wake of the industrial revolution, leading to increase in carbon dioxide level by 1900.
Cause of Concern
According to the Intergovernmental Panel on Climate Change (IPCC), global temperature is likely to rise by about 1-3.5 Celsius by the year 2100. It has also suggested that the climate might warm by as much as 10 degrees Fahrenheit over the next 100 years.
Impact of Global Warming
The sea levels are constantly rising as fresh water marshlands, low-lying cities, and islands have been inundated with seawater.
There have been changes in rainfall patterns, leading to droughts and fires in some areas, and flooding in other areas.
Ice caps are constantly melting posing a threat to polar bears as their feeding season stands reduced.
Glaciers are gradually melting.
Animal populations are gradually vanishing as there has been a widespread loss of their habitat.
As per Kyoto protocol, developed countries are required to cut back their emissions. There is a need to reduce coal-fired electricity, increase energy efficiency through wind and solar power, and also high efficiency natural gas generation
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New UN weather agency chief says rate of global warming is speeding up
FILE - Celeste Saulo, of Argentina, poses after she was elected as Secretary-General of the World Meteorological Organization (WMO) in Geneva, Switzerland, June 1, 2023, during the U.N. climate and weather agency’s congress in Geneva. (Martial Trezzini/Keystone via AP, File)
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BALTIMORE (AP) — The new chief of the World Meteorological Organization said it looks to her that the rate of human-caused climate change is accelerating and that warming has triggered more Arctic cold outbreaks in North America and Europe, weighing in on two issues that divide climate scientists.
In her first sit-down interview since taking office last month, WMO Secretary-General Celeste Saulo told The Associated Press that even though her agency said last year was 1.48 degrees Celsius (2.66 Fahrenheit) above pre-industrial levels, the world must “keep on with its ambition of trying not to reach 1.5” degrees Celsius (2.7 degrees Fahrenheit) on a longer-term basis, not just one year. “We have a trend that is really worrying. The trend is very clear.”
Saulo said the world needs to act quickly but she said there are powerful economic forces that keep that from happening.
Slow efforts to curb climate change “is not about diplomacy, I think it’s about power and economy,” Saulo said during a break at the American Meteorological Society’s meeting in Baltimore. “We are lagging behind our objectives because of our interests — economic interests — that are well beyond what our common sense, our diplomats and our scientists are pointing out.”
Last year former NASA top climate scientist James Hansen and others published a study saying the climate is not just getting warmer, but the rate of change is accelerating. A second study found ocean heat content, where much of Earth’s trapped energy is stored, is rising at a faster rate than before. Other scientists disagreed, saying warming, stoked by an El Nino, is still occurring at the predicted rate.
Saulo said she sees the acceleration Hansen is talking about, especially based on research by some WMO science teams. She said what bothers her is not knowing what it means for the future.
“We are not there in terms of our scientific understanding of the implications of this acceleration. We don’t fully understand how it is going to evolve,” Saulo said.
Saulo, who had been the head of Argentina’s meteorological office, said what worries her most is what is happening at both poles as seas warm, ice melts and society adds more heat-trapping gases.
In another area of hot debate among scientists, Saulo said she sees a link between amped up warming in the Arctic and more sudden but deep cold outbreaks in North America and Europe, often referred to as the polar vortex escaping its normal northern confines. What’s happening is that the difference between winter temperatures in the Arctic and the mid-latitudes isn’t as large as it used to be, which triggers changes in the jet stream more frequently, she said.
“There’s this huge concern, particularly in the northern hemisphere because of the continental area is exposed and so many people are living there,” Saulo said.
But what really is more important, she said, are worsening heat waves.
“Heat waves are the most killing of extreme events,” Saulo said, adding that the number of deaths are usually undercounted. Plus, heat waves have other side impacts on health, fires and air quality, she said.
She said lack of adequate monitoring and warning systems for flooding, storms, heat waves and droughts, especially in the global south, is another big problem.
“Fifty percent of our population currently does not have early warning systems in place,” Saulo said. “We need to protect them.”
Saulo is the first female WMO secretary-general, the first from the Americas and only the second one from the global south. That matters, she said, because “I bring my culture, my values and coming from the global south I think we have many things, many ideas to put on board. And I believe this is an opportunity to bring those new ideas. Not better, not worse, but different.”
With what seems like accelerated warming, more heat waves and other extremes such as floods, droughts and storms, being in charge of a global climate and weather agency can daunting, Saulo said.
“I am in a way overwhelmed, but I think we can do something,” Saulo said. “It’s a mix of being overwhelmed, but also being optimistic that there is something we can do and I can do from my position to help our society better prepare for climate change.”
Read more of AP’s climate coverage at http://www.apnews.com/climate-and-environment
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Atlantic Ocean is headed for a tipping point − once melting glaciers shut down the Gulf Stream, we would see extreme climate change within decades, study shows
Postdoctoral Researcher in Climate Physics, Utrecht University
Professor of Physics, Utrecht University
Climate Model Specialist, Utrecht University
René van Westen receives funding from the European Research Council (ERC-AdG project 101055096, TAOC).
Henk A. Dijkstra receives funding from the European Research Council (ERC-AdG project 101055096, TAOC, PI: Dijkstra).
Michael Kliphuis does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
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Superstorms, abrupt climate shifts and New York City frozen in ice. That’s how the blockbuster Hollywood movie “ The Day After Tomorrow ” depicted an abrupt shutdown of the Atlantic Ocean’s circulation and the catastrophic consequences.
While Hollywood’s vision was over the top, the 2004 movie raised a serious question: If global warming shuts down the Atlantic Meridional Overturning Circulation, which is crucial for carrying heat from the tropics to the northern latitudes, how abrupt and severe would the climate changes be?
Twenty years after the movie’s release, we know a lot more about the Atlantic Ocean’s circulation. Instruments deployed in the ocean starting in 2004 show that the Atlantic Ocean circulation has observably slowed over the past two decades, possibly to its weakest state in almost a millennium . Studies also suggest that the circulation has reached a dangerous tipping point in the past that sent it into a precipitous, unstoppable decline, and that it could hit that tipping point again as the planet warms and glaciers and ice sheets melt.
In a new study using the latest generation of Earth’s climate models, we simulated the flow of fresh water until the ocean circulation reached that tipping point.
The results showed that the circulation could fully shut down within a century of hitting the tipping point, and that it’s headed in that direction. If that happened, average temperatures would drop by several degrees in North America, parts of Asia and Europe, and people would see severe and cascading consequences around the world.
We also discovered a physics-based early warning signal that can alert the world when the Atlantic Ocean circulation is nearing its tipping point.
The ocean’s conveyor belt
Ocean currents are driven by winds, tides and water density differences .
In the Atlantic Ocean circulation, the relatively warm and salty surface water near the equator flows toward Greenland. During its journey it crosses the Caribbean Sea, loops up into the Gulf of Mexico, and then flows along the U.S. East Coast before crossing the Atlantic.
This current, also known as the Gulf Stream, brings heat to Europe. As it flows northward and cools, the water mass becomes heavier. By the time it reaches Greenland, it starts to sink and flow southward. The sinking of water near Greenland pulls water from elsewhere in the Atlantic Ocean and the cycle repeats, like a conveyor belt .
Too much fresh water from melting glaciers and the Greenland ice sheet can dilute the saltiness of the water, preventing it from sinking, and weaken this ocean conveyor belt . A weaker conveyor belt transports less heat northward and also enables less heavy water to reach Greenland, which further weakens the conveyor belt’s strength. Once it reaches the tipping point , it shuts down quickly.
What happens to the climate at the tipping point?
The existence of a tipping point was first noticed in an overly simplified model of the Atlantic Ocean circulation in the early 1960s . Today’s more detailed climate models indicate a continued slowing of the conveyor belt’s strength under climate change. However, an abrupt shutdown of the Atlantic Ocean circulation appeared to be absent in these climate models.
This is where our study comes in. We performed an experiment with a detailed climate model to find the tipping point for an abrupt shutdown by slowly increasing the input of fresh water.
We found that once it reaches the tipping point, the conveyor belt shuts down within 100 years. The heat transport toward the north is strongly reduced, leading to abrupt climate shifts.
The result: Dangerous cold in the North
Regions that are influenced by the Gulf Stream receive substantially less heat when the circulation stops. This cools the North American and European continents by a few degrees.
The European climate is much more influenced by the Gulf Stream than other regions. In our experiment, that meant parts of the continent changed at more than 5 degrees Fahrenheit (3 degrees Celsius) per decade – far faster than today’s global warming of about 0.36 F (0.2 C) per decade. We found that parts of Norway would experience temperature drops of more than 36 F (20 C). On the other hand, regions in the Southern Hemisphere would warm by a few degrees.
These temperature changes develop over about 100 years. That might seem like a long time, but on typical climate time scales, it is abrupt.
The conveyor belt shutting down would also affect sea level and precipitation patterns, which can push other ecosystems closer to their tipping points . For example, the Amazon rainforest is vulnerable to declining precipitation . If its forest ecosystem turned to grassland, the transition would release carbon to the atmosphere and result in the loss of a valuable carbon sink, further accelerating climate change.
The Atlantic circulation has slowed significantly in the distant past . During glacial periods when ice sheets that covered large parts of the planet were melting, the influx of fresh water slowed the Atlantic circulation, triggering huge climate fluctuations.
So, when will we see this tipping point?
The big question – when will the Atlantic circulation reach a tipping point – remains unanswered. Observations don’t go back far enough to provide a clear result. While a recent study suggested that the conveyor belt is rapidly approaching its tipping point , possibly within a few years, these statistical analyses made several assumptions that give rise to uncertainty.
Instead, we were able to develop a physics-based and observable early warning signal involving the salinity transport at the southern boundary of the Atlantic Ocean. Once a threshold is reached, the tipping point is likely to follow in one to four decades.
The climate impacts from our study underline the severity of such an abrupt conveyor belt collapse. The temperature, sea level and precipitation changes will severely affect society, and the climate shifts are unstoppable on human time scales.
It might seem counterintuitive to worry about extreme cold as the planet warms, but if the main Atlantic Ocean circulation shuts down from too much meltwater pouring in, that’s the risk ahead.
This article was updated on Feb. 11, 2024, to fix a typo: The experiment found temperatures in parts of Europe changed by more than 5 F per decade.
- Climate change
- Global warming
- Extreme weather
- Atlantic Ocean
- Climate models
- Greenland ice sheet
- Ocean circulation
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The sun is mighty, but modern climate change is caused by human activity | Fact check
The claim: Post implies modern climate change is caused by the sun
A Jan. 18 Facebook post ( direct link , archive link ) shows an image of the sun and the solar system planets. The sun is labeled "THIS IS WHAT CONTROLS THE CLIMATE," while a comparatively tiny dot that appears to be Earth is labeled "YOU LIVE HERE."
Some commenters appeared to take the post as evidence that humans are not responsible for modern climate change.
"Oh - I thought it was my 1 litre Ford," wrote one such user.
Another user posted a gif of Greta Thunberg saying "How dare you!" a line from her highly publicized 2019 speech on climate change .
The image, which was posted to the Facebook group "Climate Con," was shared more than 600 times in a month.
More from the Fact-Check Team: How we pick and research claims | Email newsletter | Facebook page
Our rating: Missing context
The implied claim is wrong. While the sun significantly impacts Earth's climate, it is not responsible for modern climate change. There is extensive evidence that greenhouse gas emissions by human activity are causing climate change.
Modern climate change is driven by CO2 emissions, not changes in the sun
There has not been a change in the state of the sun that could explain modern climate change, according to NASA.
"The sun can influence Earth’s climate, but it isn’t responsible for the warming trend we’ve seen over recent decades," the agency reports. "We know subtle changes in Earth’s orbit around the sun are responsible for the comings and goings of the ice ages. But the warming we’ve seen in recent decades is too rapid to be linked to changes in Earth’s orbit and too large to be caused by solar activity ."
Since the late 1970s, researchers have been using satellites to track the amount of solar energy striking the Earth and have not detected an upward trend, according to NASA. However, the rate of global warming has accelerated significantly over this timeframe .
Can we count on renewable energy? Four ways wind, solar and water can power the US
In addition, if the sun was causing modern global warming, all layers of the atmosphere should be warming, NASA reports . But this is not what is happening.
Instead, the lower level of the atmosphere − the troposphere − is warming, while an upper level − the stratosphere − is cooling. This is partially because more heat is being retained in the troposphere due to greenhouse gases, such as CO2.
Greenhouse gases emitted by human activity are changing Earth's climate
While there is no evidence that modern climate change is caused by the sun, decades of research by generations of scientists have clearly demonstrated that it is caused by accumulating greenhouse gases emitted by human activity.
In the mid-1800s, scientists showed that greenhouse gases such as CO2 could slow the escape of heat into space . Researchers have since measured significant increases in global temperatures and atmospheric greenhouse gas levels .
"The amount of warming we see matches what we expect based on the increased CO2 we've added," Josh Willis , a NASA climate scientist, previously told USA TODAY . "The timing of the warming matches the timing of the CO2 increase caused by people. Not only that, the timing of global sea level rise matches the CO2 increase."
Global sea levels are rising because sea water expands as it warms, and additional water is being added to the ocean basins as glaciers and polar ice melt .
Additionally, because researchers have been publishing climate projections for decades, they've had the opportunity to test whether their understanding of greenhouse gas physics and planetary sciences holds up over time. Their models have been fairly accurate in predicting subsequent warming, according to an analysis by Harvard researchers and another by Carbon Brief .
Researchers can also tell that the excess CO2 causing the warming was emitted by humans. This is because atmospheric CO2 contains a disproportionate amount of the type of carbon found in fossil fuels and because the amount of excess CO2 in the atmosphere matches the amount released by human activity once other natural processes are taken into account.
"Scientists have looked for other sources of heat, cycles of the sun, volcanos on the sea floor and pretty much everything else you can think of," Willis said. "Nothing besides humans burning fossil fuels can explain all of these things."
USA TODAY reached out to the Facebook user who shared the post for comment but did not immediately receive a response.
Our fact-check sources:
- USA TODAY, Aug. 17, 2023, Greenhouse gases, not Milankovitch cycles, drive modern global warming | Fact check
- USA TODAY, Jan. 20, 2023, Fact check: Global warming caused by greenhouse gas emissions, not mysterious ocean warming
- USA TODAY, Dec. 20, 2023, How we know humans are causing warming: A brief history of climate science | Fact check
- USA TODAY, Nov. 28, 2022, Fact check: Earth's warming well documented, other planets' climate data limited
- Australian Department of Climate Change, Energy and the Environment and Water, accessed Feb. 9, Understanding climate change
- The Conversation, July 21, 2020, John Tyndall: the forgotten co-founder of climate science
- NASA Vital Signs of the Planet, accessed Feb. 9, Causes
- NASA Vital Signs of the Planet, accessed Feb. 9, Global temperature
- NASA Vital Signs of the Planet, accessed Feb. 9, Carbon dioxide
- NASA Vital Signs of the Planet, accessed Feb. 9, Ocean warming
- NASA Vital Signs of the Planet, accessed Feb. 9, Ice sheets
- NASA Vital Signs of the Planet, accessed Feb. 9, Sea level
- NASA Earth Observatory, accessed Feb. 9, World of Change: Global Temperatures
- NASA, Feb. 27, 2020, Why Milankovitch (Orbital) Cycles Can't Explain Earth's Current Warming
- NASA, Feb. 27, 2020, Milankovitch (Orbital) Cycles and Their Role in Earth's Climate
- NASA Global Climate Change, accessed Feb. 14, Is the sun causing global warming?
- NASA Global Climate Change, Sept. 6, 2019, What Is the Sun's Role in Climate Change?
- NASA Global Climate Change, July 10, 2020, Graphic: Temperature vs solar activity
- NOAA, Sept. 1, 2009, Climate Change: Incoming Sun l ight
- NOAA, Oct. 12, 2022, How do we know the build-up of carbon dioxide in the atmosphere is caused by humans?
- NOAA, Jan. 18, Climate Change: Global Temperature
- Environmental Protection Agency, July 2022, Climate Change Indicators: Heat Waves
- EPA, accessed Feb. 9, Climate Change Indicators: Weather and Climate
- Carbon Brief, April 28, 2021, Melting glaciers drove ‘21% of sea level rise’ over past two decades
- Carbon Brief, Oct. 5, 2017, Analysis: How well have climate models projected global warming?
- The Harvard Gazette, Jan. 12, 2023, Exxon disputed climate findings for years. Its scientists knew better
- Science, Jan. 13, 2023, Assessing ExxonMobil’s global warming projections
- University of California Los Angeles, Aug. 21, Stratospheric cooling: The concerning flip side of global warming
Thank you for supporting our journalism. You can subscribe to our print edition, ad-free app or e-newspaper here .
USA TODAY is a verified signatory of the International Fact-Checking Network, which requires a demonstrated commitment to nonpartisanship, fairness and transparency. Our fact-check work is supported in part by a grant from Meta .
Controversial climate change study claims we'll breach 2 C before 2030
If the new study is correct, global warming is at least a decade further ahead than we thought. But other scientists say it is filled with errors and inconsistencies.
A new study has claimed that we may breach the 2 degrees Celsius (3.6 degrees Fahrenheit) climate change increase threshold by the late 2020s — almost two decades earlier than current projections.
The study, published Feb. 5 in the journal Nature Climate Change , claims global surface temperatures had increased by 1.7 C (3 F) above pre-industrial averages by the year 2020.
However, other scientists have questioned the findings, saying that there are flaws in the work.
Global warming of 2 C is considered an important threshold — warming beyond this greatly increases the likelihood of devastating and irreversible climate breakdown. Under the 2015 Paris Agreement, nearly 200 countries pledged to limit global temperature rises to ideally 1.5C and safely below 2C.
"The big picture is that the global warming clock for emissions reductions to minimize the risk of dangerous climate change has been brought forward by at least a decade," lead author Malcolm McCulloch , a coral reef expert at The University of Western Australia, said at a news conference on Thursday (Feb. 1). "This is a major change to the thinking about global warming."
A huge issue in climate science is where to set the pre-industrial baseline, before fossil fuel burning kickstarted warming. Until the 20th century, ocean temperatures records were a sporadic and non-standardized patchwork of millions of observations collected by sailors to chart courses through seas.
Related: World must act now to defuse 'climate time bomb,' UN scientists warn
To weed out erroneous past recordings, climate scientists have previously turned to natural records of temperature stored in ocean animals such as coral, in ice and sediment cores or inside tree grains.
However, scientists still have no consensus on the amount of post-industrial warming. A recent analysis using the U.S. National Oceanic and Atmospheric Administration's (NOAA) 2023 dataset suggested Earth had warmed by 1.34 C (2.4 F) above the 1850 to 1900 average, while data from the U.K. Met Office placed it at 1.54 C (2.7 F).
Sponge for knowledge
To search for a better record of 19th-century temperatures, the researchers behind the new study looked at a sponge species called Ceratoporella nicholsoni in the Caribbean Sea. Known for their rock-hard exoskeletons, C. nicholsoni can live for more than a thousand years, assiduously adding layers to their limestone shells by drawing strontium and calcium carbonate from seawater.
The ratio of strontium to calcium at a particular part in a sclerosponge's skeleton decreases as ocean waters warm , enabling the scientists to measure 300 years of temperature records in cross-sections of their bodies — similar to reading tree rings.
After collecting and analyzing multiple sponges from depths between 100 to 300 feet (30 to 90 meters), the researchers produced a record of temperatures they say scales with temperatures across the entire planet’s oceans.
Related: Gulf Stream current could collapse in 2025, plunging Earth into climate chaos: 'We were actually bewildered'
Their results suggest that warming began in the 1860s, about four decades earlier than the UN's Intergovernmental Panel on Climate Change (IPCC) estimates.
By 1990, they found, global temperatures had increased by 0.9 C (1.6 F) compared with before their newly defined pre-industrial era. In comparison, the IPCC estimates 0.4 C (0.7 F) of warming by this time.
According to the study, if current rates of heating continue, 2 C warming will be reached by the end of the 2020s, with 2.5 C (4.5 F) of warming by 2040.
Other climate scientists have criticized the new study's findings. The researchers say they assumed that oceans are well-mixed and that the water temperatures recorded by the sponges came from depths that mainly respond to heating from the sun.
But others argue that the ocean is still a highly complex engine that is far from uniform in temperature.
"Skepticism is warranted here. In my view it begs credulity to claim that the instrumental record is wrong based on paleosponges from one region of the world," Michael Mann , the director of the Earth System Science Center at the University of Pennsylvania, told Live Science. "It honestly doesn't make any sense to me."
Camille Parmesan , an ecologist at the University of Texas, Austin and a coordinating lead author for the IPCC's 6th Assessment Report , noted that the temperature of one part of the ocean is unlikely to represent ocean temperatures elsewhere. "You cannot extrapolate from the Caribbean to the whole of the world's oceans," Parmesan told Live Science.
And David Thornalley , a professor of ocean and climate science at University College London, also criticized the researchers' decision to calibrate their sponge data with global sea surface temperatures, rather than the sea surface temperatures for the region the sponges came from.
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"The study fails to support its global claims with robust evidence, and it fails by a huge margin," Jochem Marotzke , a professor of climate science and the director of the Max Planck Institute for Meteorology in Germany, told Live Science. "The extrapolation from that little piece of ocean to the global is wholly unbelievable." The claim that the Caribbean's temperature increase since the 1860s comes solely from the sun, rather than ocean mixing, also beggars belief, he added.
The researchers, meanwhile, insist that Caribbean sea surface temperatures trends are globally proportional — citing a 2018 paper.
Even if the conclusions of the study are questionable, scientists said the study could still contribute as a piece in the global jigsaw of climatic information, especially as rapid climate change is approaching regardless of the mix of evidence used or where the baseline is set.
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Ben Turner is a U.K. based staff writer at Live Science. He covers physics and astronomy, among other topics like tech and climate change. He graduated from University College London with a degree in particle physics before training as a journalist. When he's not writing, Ben enjoys reading literature, playing the guitar and embarrassing himself with chess.
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- Epicenter & 4 more I don't believe the 2º C over pre-industrial times average temperatures limit will be crossed before 2030, I guess it has been already crossed. For its more immediate and more economy devastating consequences, I suggest reading: 'Sea Changes', Science, 2015. About health issues, I won't trust much the WHO, it took several weeks for them to realize COVID is a respiratory disease, and Respiratory Isolation measures, direct and inverse, had to be implemented. Vaccines for a new disease do not come in one day. Blessings + Sea-level rise due to polar ice-sheet mass loss during past warm periods Reply
Epicenter & 4 more said: it took several weeks for them to realize COVID is a respiratory disease,
- prrawlins CO2 is not a green house gas. Science shows this from the ice core drilling that the earth's temp changed up and then lower at times before CO2 changed . Also the amount of CO2 created by mankind's activitiy is not enought to change the earth's CO2 level to anything accounting for any change: https://intention6.wordpress.com/2023/05/21/carbon/ Reply
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