A debate over climate science triggered by comments from a UK political figure has drawn attention to how declining air pollution may be accelerating global warming. While the original claim that cleaner air rather than carbon dioxide drives temperature increases was incorrect, the underlying scientific phenomenon is genuine and increasingly recognized by climate researchers.
Fossil fuel combustion produces both carbon dioxide and sulphur pollution. Carbon dioxide traps heat in the atmosphere, while sulphur particles form aerosols that reflect sunlight back into space, counteracting some warming. Decades of clean-air policies—including measures like the US Acid Rain Program and new shipping regulations—have significantly reduced sulphur emissions across Europe, North America, and China. However, carbon dioxide levels remain near record highs. Scientists now believe that as sulphur pollution has declined, its cooling effect has diminished, allowing more of the underlying warming from greenhouse gases to become apparent.
Researchers at ETH Zurich and other institutions have analyzed temperature data while accounting for natural climate fluctuations such as El Niño. Their findings indicate that the rate of global warming has accelerated in recent years. The Met Office has stated that 2027 is “very likely” to become the warmest year on record, following three consecutive record-breaking warm years. Studies suggest declining aerosol pollution may be contributing approximately 0.05 to 0.1 degrees Celsius of additional warming per decade, with particularly strong effects in regions where sulphur emissions have fallen most sharply, such as western-central Europe.
While aerosols are playing a measurable role in recent warming acceleration, they account for only part of the observed increase. Greenhouse gases remain the dominant warming factor, currently adding approximately 0.2 degrees Celsius per decade globally. Scientists emphasize that cleaner air is not causing the underlying warming but rather removing some of the cooling effect that had previously masked the full warming impact of greenhouse gases. The continuing investigation into what else may be driving accelerated warming involves examining Earth’s overall energy balance—the difference between energy absorbed from the Sun and heat lost to space.
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