Issue Aerosol trade-off between cleaner air and unmasked warming

Summary

Aerosols are fine particles from fossil fuel combustion, industry, transport and biomass burning that influence sunlight, clouds, rainfall and atmospheric circulation. Some, like sulfates, reflect sunlight and cool the planet, while others, like black carbon, absorb it and warm the air, making their climate effects complex and regionally varied. Over recent decades, air quality efforts in higher-income regions have cut emissions, and global anthropogenic aerosol loading is falling. The report finds that this decline lowers air pollution and health risks and benefits ecosystems, yet may accelerate global warming by removing the cooling some particles provide. Managing aerosol emissions thus involves a trade-off between health gains and unmasking greenhouse warming that had been partly hidden. The report observes that this complicates climate policy.