Climate sensitivity may be higher than models assumed, accelerating warming

September 9, 2026 at 04:11 AM2 min

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Scientists increasingly believe the loss of sulphur aerosol cooling is slightly speeding up global warming. The past three years were the three warmest ever recorded, and the Met Office says 2027 is very likely to replace 2024 as the warmest year on record. The debate follows a public row over whether cleaner air, rather than carbon dioxide, is behind higher temperatures.

Key Facts

The past three years were the three warmest ever recorded, and the Met Office says 2027 is very likely to replace 2024 as the warmest year on record.
Reto Knutti and his team at ETH Zurich found that the rate of warming has accelerated after stripping out natural fluctuations like El Niño.
Sulphur emissions are falling sharply due to clean-air policies such as the US Acid Rain Program, while carbon dioxide emissions remain near record highs.
A separate study published this year reached a similar conclusion about accelerated warming after accounting for several major natural influences.

Aerosol Cooling Loss

Burning coal and oil releases sulphur dioxide, which forms tiny particles known as sulphate aerosols that reflect sunlight back into space. Clean-air policies around the world, like the US Acid Rain Program in the early 1990s, have sharply reduced sulphur emissions. Scientists increasingly believe the loss of that cooling effect is slightly speeding up global warming. Carbon dioxide emissions remain near record highs even as sulphur pollution falls.

Accelerated Warming Evidence

Reto Knutti, a professor of climate physics at ETH Zurich and former IPCC co-ordinating lead author, says the rate of warming has accelerated after removing natural fluctuations. A separate study published this year reached a similar conclusion after accounting for several major natural influences. The past three years were the three warmest ever recorded, and the Met Office says 2027 is very likely to replace 2024 as the warmest year on record. El Niño and other natural fluctuations can temporarily push global temperatures higher, but the underlying trend appears to be accelerating.