According to a Washington Post analysis, the fastest warming rate on record occurred in the last 30 years. The Post used a dataset from NASA to analyze global average surface temperatures from 1880 to 2025.
“We’re not continuing on the same path we had before,” said Robert Rohde, chief scientist at Berkeley Earth. “Something has changed.”
For about 40 years — from 1970 to 2010 — global warming proceeded at a fairly steady rate. As humans continued to pump massive amounts of greenhouse gases into the atmosphere, the world warmed at about 0.19 degrees Celsius per decade, or around 0.34 degrees Fahrenheit.
Then, that rate began to shift. The warming rate ticked up a notch. Temperatures over the past decade have increased by close to 0.27 degrees C per decade — about a 42 percent increase.
Those data — combined with the last few years of record heat — have convinced many researchers that the world is seeing a decisive shift in how temperatures are rising. The last 11 years have been the warmest years on record; according to an analysis by Berkeley Earth, if we assume a constant rate of warming since the 1970s, the last three years have a less than 1-in-100 chance of occurring solely due to natural variability.
“There is greater acceptance now that there is a detectable acceleration of warming,” said Zeke Hausfather, a climate scientist and the research lead at the payments company Stripe.
Even as the United States languishes under a frigid cold snap, the rest of the world is still experiencing unusually warm temperatures. Nuuk, Greenland, for example, saw temperatures in January more than 20 degrees Fahrenheit above average. Parts of Australia, meanwhile, have seen temperatures push past 120 degrees Fahrenheit amid a record heat wave.
Some of that change was predicted by climate models. For decades, a portion of the warming unleashed by greenhouse gas emissions was “masked” by sulfate aerosols. These tiny particles cause heart and lung disease when people inhale polluted air, but they also deflect the sun’s rays. Over the entire planet, those aerosols can create a significant cooling effect — scientists estimate that they have canceled out about half a degree Celsius of warming so far.
But beginning about two decades ago, countries began cracking down on aerosol pollution, particularly sulfate aerosols. Countries also began shifting from coal and oil to wind and solar power. As a result, global sulfur dioxide emissions have fallen about 40 percent since the mid-2000s; China’s emissions have fallen even more. That effect has been compounded in recent years by a new international regulation that slashed sulfur emissions from ships by about 85 percent.
That explains part of why warming has kicked up a bit. But some researchers say that the last few years of record heat can’t be explained by aerosols and natural variability alone. In a paper published in the journal Science in late 2024, researchers argued that about 0.2 degrees C of 2023’s record heat — or about 13 percent — couldn’t be explained by aerosols and other factors. Instead, they found that the planet’s low-lying cloud cover had decreased — and because low-lying clouds tend to reflect the sun’s rays, that decrease warmed the planet.
Clouds have long been one of the greatest uncertainties in climate science. Clouds are probably helping to cool the Earth, like aerosols, but how much is an open question. “Pretty much every climate model agrees that it’s a cooling effect, but the size of that cooling effect is quite uncertain,” said Chris Smith, a research fellow at the University of Leeds and the International Institute for Applied Systems Analysis.
That shift in cloud cover could also be partly related to aerosols, since clouds tend to form around particles in the atmosphere. But some researchers also say it could be a feedback loop from warming temperatures. If temperatures warm, it can be harder for low-lying clouds to form.
If most of the current record warmth is due to changing amounts of aerosol pollution, the acceleration would stop once aerosol pollutants reach zero — and the planet would return to its previous, slower rate of warming.
But if it’s due to a cloud feedback loop, the acceleration is likely to continue — and bring with it worsening heat waves, storms and droughts. “If there is a strengthening cloud feedback — a positive cloud feedback associated with warming — that’s going to persist,” Hausfather said.
Even a few years ago, many researchers weren’t ready to claim that warming was accelerating. Some are still waiting for more data. “It’s still too early to definitively conclude there’s an increase in the rate of warming,” Smith said. While the changes in aerosols make sense intuitively, he said, he wants to see a few years of additional data.
Robert Rohde for Berkeley Earth:
Over the previous 50 years, global warming has preceded in an almost linear fashion, consistent with an almost linear increase in the total greenhouse gas forcing. The warming spike in 2023 to 2025 suggests that the past warming rate is no longer a reliable predictor of the future, and additional factors have created conditions for faster warming, at least in the short-term.
Ripple et al in One Earth (Journal publication):
Are we now at risk of crossing planetary tipping points and triggering a hothouse Earth trajectory? Science doesn’t have a precise answer, but this question requires urgent research, including exploring other hypotheses involving glacial/interglacial cycling and Holocene stability, and working to better understand climate dynamics. While the exact risk is uncertain, it is clear that current climate commitments, which have us on track for roughly 2.8°C peak warming by 2100,7 are insufficient and greater climate mitigation efforts are needed.