A debate over climate science on social media highlighted a scientifically real phenomenon: the role of air pollution in masking some warming effects. While fossil fuel combustion releases carbon dioxide, which traps heat, it also produces sulphur dioxide that forms tiny particles in the atmosphere. These sulphate aerosols reflect sunlight back to space, partially offsetting warming. As countries implemented clean-air policies over recent decades—including regulations on power plants and shipping emissions—sulphur pollution levels fell sharply while carbon dioxide emissions remained near record highs.
Researchers at institutions including ETH Zurich and the University of Leeds have found that the removal of this cooling effect is slightly accelerating global warming. Studies accounting for natural climate variations like El Niño suggest the underlying rate of warming has increased. Climate physicist Reto Knutti noted the acceleration is “pretty clear” when natural fluctuations are stripped away. The effect appears strongest in regions where air quality improvements have been most dramatic, with one study estimating declining sulphur pollution has added approximately half a degree to summer warming in western-central Europe since 1980.
However, experts emphasize that cleaner air explains only part of the recent acceleration. Professor Piers Forster estimates declining aerosols may be adding 0.05 to 0.1 degrees Celsius of warming per decade, while greenhouse gases are currently adding around 0.2 degrees per decade. The aerosol effect represents “a very significant contribution” but remains substantially less important than greenhouse gas warming. Scientists continue investigating what other factors might be influencing Earth’s energy balance and the rate at which the planet absorbs solar energy versus radiating heat back into space.
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