Recent record temperatures have reignited debate about the mechanisms driving climate change, particularly regarding the role of air pollution and its effects on planetary warming.
While carbon dioxide remains the primary driver of global warming, fossil fuel combustion also produces sulphur dioxide, which forms particles that reflect sunlight back into space, providing a cooling effect. Over recent decades, clean-air policies in the United States, Europe, China and other regions have significantly reduced sulphur emissions to protect human health and prevent acid rain. However, scientists increasingly recognize that this reduction in sulphate aerosols is removing a natural brake on warming, allowing more sunlight to reach Earth’s surface.
Research from institutions including ETH Zurich and the Norwegian climate research institute indicates that declining aerosol pollution may be contributing an additional 0.05 to 0.1 degrees Celsius of warming per decade. Professor Piers Forster of the University of Leeds estimates this aerosol effect is “very significant,” though greenhouse gas emissions remain the dominant warming factor at approximately 0.2 degrees Celsius per decade. The recent three warmest years on record and projections that 2027 could become the warmest year yet have prompted closer examination of whether underlying climate sensitivity to greenhouse gases is greater than previously understood.
While cleaner air accounts for some of the recent acceleration in warming, scientists emphasize this reflects the removal of masking effects rather than a new source of heat. The cooling properties of aerosols persist only days or weeks in the atmosphere, whereas carbon dioxide remains for centuries. Understanding this distinction proves important for interpreting current temperature trends and assessing the actual pace of climate change independent of natural variability like El Niño events.
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