Pollution from the combustion of fossil fuels and wood has contributed to climate change in complex ways, with some pollutants causing cooling and others causing warming, accompanied by effects on patterns of atmospheric circulation and precipitation. To better understand these complex relationships, the Atmospheric Chemistry Climate Model Intercomparison Project, part of the international 5th-phase Coupled Model Intercomparison Project (CMIP5), conducted a series of pollution-focused modeling experiments to reveal spatial patterns, sectoral influences, chemical components, and climate impacts—all critical for understanding how Earth’s climate is likely to respond to different energy pathways.

These studies, conducted by academic research institutions and modeling centers supported by NASA, DOE, NOAA, and NSF, considered both model results and instrumental measurements. They found that aerosol pollution peaked globally around the 1980s, and that the solar radiation-blocking effect of the aerosols was strong enough to mask the progression of global warming in most industrialized parts of the world. After 1980, global warming was “unmasked” in most regions following declines in aerosol pollution—except in eastern and southeastern Asia, where aerosol pollution continues to create a localized cooling effect and has been shown to impact monsoon patterns. To learn more about results from the Atmospheric Chemistry Climate Model Intercomparison Project, visit: http://go.usa.gov/8VpY