Trend Global aerosol imbalance easing while aerosol pollution shifts regionally

Summary

The aerosol boundary is measured by the difference in aerosol optical depth between the northern and southern hemispheres, which at 0.07 sits below the 0.1 boundary and inside the safe space. The gap has generally narrowed since 2010, reflecting falling emissions as higher-income regions improved their air quality. In parts of Asia and Africa, however, rapid industrial growth and biomass burning keep emissions high or push them higher. Aerosols influence sunlight, clouds, rainfall and circulation, mixing particles such as sulfates that reflect light and cool with others such as black carbon that absorb heat. The report observes that declining global loading reduces air pollution and health risks but may speed warming by removing the cooling some particles provide. It adds that the global indicator misses regional risks, and South Asia already exceeds its proposed regional boundary.