Recent record-breaking temperatures have sparked debate about the mechanisms driving global warming. While carbon dioxide remains the primary driver, a lesser-known cooling effect from sulphur pollution plays a significant role in Earth’s climate system. Sulphur dioxide from burning fossil fuels creates tiny particles that reflect sunlight back to space, partially offsetting greenhouse gas warming—similar to dust on greenhouse windows.
Over the past several decades, clean-air policies in Europe, North America, China, and the shipping industry have substantially reduced sulphur emissions. These regulations were designed to protect human health and prevent acid rain damage to ecosystems. However, as sulphur pollution has declined, its cooling effect has diminished almost immediately, since sulphate aerosols persist in the atmosphere for only days or weeks, unlike carbon dioxide which remains for centuries.
Researchers at ETH Zurich and other institutions have analyzed climate data while accounting for natural fluctuations like El Niño to determine underlying warming trends. According to climate scientists, the rate of warming has accelerated in recent years. One estimate suggests declining aerosol pollution has added approximately half a degree to summer warming in western-central Europe since 1980. Currently, this effect may contribute around 0.05 to 0.1 degrees Celsius of additional warming per decade.
However, aerosols explain only part of the recent acceleration. Greenhouse gases remain the dominant factor, contributing roughly 0.2 degrees Celsius per decade globally—substantially more than the aerosol effect. Scientists describe the phenomenon as cleaner air removing a masking effect that previously partially concealed the full warming impact of greenhouse gases. Researchers continue examining Earth’s overall energy balance, measuring sunlight absorption and heat loss, to fully understand the complex interactions driving current climate trends.
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