What Happens When Extreme Heat and Air Pollution Collide

Throughout the thousands of pages of the IPCC’s AR6 report, the authors detailed some of the most alarming climate impacts, including the deeply intertwined relationship between global warming and poor air quality.

Put simply, air pollution levels spike when temperatures rise. This happens in a variety of ways. High temperatures can lead to more frequent droughts and more intense wildfires, both of which increase particulate matter (PM10 and PM2.5). Wildfires also release large amounts of black carbon, nitrogen oxides (NOx), carbon monoxide (CO) and other volatile organic compounds (VOCs). Heat also accelerates biological processes responsible for the degradation of organic waste and wastewater, releasing both air pollutants and greenhouse gases into the air.

Certain pollutants, however, actually feed on the heat. Ground-level (or tropospheric) ozone, an often overlooked but deadly pollutant, forms when VOCs, including methane, and NOx emissions from vehicles, industrial facilities, waste and agricultural burning and other sources chemically react through exposure to sunlight. Warmer temperatures accelerate these reactions, leading to increased ozone production, which manifests as a harmful haze. As a result, during hotter, dryer, less windy months — and especially during heat waves — ground-level ozone can reach dangerous levels in cities.

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