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, meaning major climate catastrophes could happen sooner than expected.
Earth was warming by about 0.18°C per decade prior to 2013-14. Since then, it has been heating up by about 0.36°C per decade, according to an analysis by Stefan Rahmstorf at the University of Potsdam, Germany, and his colleagues.
If warming continues at this rate, humanity could breach the Paris Agreement goal of limiting warming to 1.5°C in 2028, even sooner than other research has projected.
“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 US, is trying to halt global warming, reduce it, and that’s why the fact that it’s now actually doing the opposite, accelerating, is of great concern.”
After a string of record-hot years, climate scientists began widely debating in 2023 whether global warming is speeding up. But natural fluctuations, such as the El Niño climate phase, which caused additional warming in 2023 and 2024, made it difficult to tell if the faster rise in temperatures 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 that attribution with 98 per cent confidence.
The team analysed five different datasets of global temperature, some of which show a higher number. According to the analysis of the dataset from the European Centre for Medium-Range Weather Forecasts, global warming could reach 1.5°C above the preindustrial period this year, based on a 20-year average.
Warm-water coral reefs are starting to collapse, and breaching 1.5°C risks crossing other tipping points like irreversible melting of Greenland and west Antarctica and the dieback of the Amazon rainforest.
Many scientists think the acceleration in global heating was caused mainly by a crackdown in 2020 on sulphur dioxide in shipping emissions. While that substance is harmful to human health, it also formed a haze of aerosols that was blocking sunlight and cooling the planet.
Now that this sunlight has been unblocked, the warming rate may slow down, but it’s hard to say for sure, says Rahmstorf. The transition away from fossil fuels will continue to diminish air pollution that is masking warming.
“There will be further aerosol reductions, [but] probably not as rapid as those shipping emissions were reduced,” he says. “It’s quite possible that the warming rate 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 cycles of high sunspots. After excluding these effects, they fitted two types of curve to global temperatures, both of which showed an acceleration in warming, although at different times.
It’s unlikely, however, that the researchers were able to completely remove the temperature effects of El Niño, volcanoes and sunspots, according to Zeke Hausfather at Berkeley Earth in California. That means they could be slightly overestimating how much global warming has sped up. But the study does offer convincing proof it has quickened, he says.
“The broader takeaway is that we have strong evidence for acceleration even if we don’t know precisely how much the rate of warming has increased as of yet,” Hausfather says. “We will need to wait a few more years to get more data.”
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