Ocean warming has led to widespread bleaching of warm water corals
Sirachai Arunrugstichai/Getty Images
Global warming has accelerated and is now happening twice as fast as in previous decades, which means that major climate disasters can happen sooner than expected.
The Earth warmed by about 0.18 °C per decade before 2013-14. Since then, it has warmed by about 0.36°C per decade, according to an analysis by Stefan Rahmstorf of the University of Potsdam, Germany, and his colleagues.
If warming continues at this rate, humanity could breach the Paris Agreement’s goal of limiting warming to 1.5°C by 2028, even sooner than other research has estimated.
“Every tenth of a degree matters and makes the impact of global warming worse in terms of extreme weather events, in terms of ecosystem impacts, also the risk of crossing tipping points,” says Rahmstorf. “The world, apart from the United States, is trying to stop global warming, reduce it, and that’s why the fact that now it’s actually doing the opposite, accelerating, is of great concern.”
After a series of record hot years, climate scientists began to discuss in 2023 whether global warming is increasing. But natural fluctuations, such as the El Niño climate phase, which caused further warming in 2023 and 2024, made it difficult to tell whether the faster temperature increase was due to climate change or just random weather.
Rahmstorf’s study is the first to find a statistically significant acceleration due to climate change, making this attribution 98 percent certain.
The team analyzed five different data sets of global temperature, some of which show a higher number. According to the analysis of the data set by the European Center for Medium-Range Weather Forecasts, global warming could reach 1.5 °C above the pre-industrial period this year, based on a 20-year average.
Warm-water coral reefs are beginning to collapse, and a breach of 1.5 °C risks crossing other tipping points such as the irreversible melting of Greenland and West Antarctica and the decline of the Amazon rainforest.
Many scientists believe that the acceleration in global warming was mainly caused by a breach of sulfur dioxide in shipping emissions in 2020. Although the substance is harmful to human health, it also formed a haze of aerosols that blocked sunlight and cooled the planet.
Now that this sunlight has been released, the rate of warming may slow, but it is difficult to say anything for sure, says Rahmstorf. The transition away from fossil fuels will continue to reduce air pollution that masks warming.
“There will be further reductions of aerosols, (but) probably not as quickly as emissions from shipping were reduced,” he says. “It is quite possible that the rate of warming will be lower in the next decade.”
In addition to El Niño, the authors estimated the effects of volcanic eruptions, which also create sun-blocking haze, and increased solar radiation during high sunspot cycles. After excluding these effects, they fitted two types of curves to global temperatures, both of which showed an acceleration in warming, but at different times.
However, it is unlikely that scientists were able to completely remove the temperature effects of El Niño, volcanoes and sunspots, according to Zeke Hausfather at Berkeley Earth in California. This means that they may slightly overestimate how much global warming has increased. But the study provides convincing evidence that it has become faster, he says.
“The broader takeaway is that we have strong evidence for acceleration even though we don’t know exactly how much the rate of warming has increased yet,” says Hausfather. “We have to wait a few more years to get more data.”
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