Asian aerosols: Current and year 2030 distributions and implications to human health and regional climate change

Aerosol distributions in Asia calculated over a 4-year period and constrained by satellite observations of aerosol optical depth (AOD) are presented. Vast regions in Asia that include >80% of the population have PM_2.5 concentrations that exceed on an annual basis the WHO guideline of 10 μ g/m³, often by factors of 2 to 4. These high aerosol loadings also have important radiative effects, causing a significant dimming at the surface, and mask ∼45% of the warming by greenhouse gases. Black carbon (BC) concentrations are high throughout Asia, representing 5-10% of the total AOD, and contributing significantly to atmospheric warming (its warming potential is ∼55% of that due to CO₂). PM levels and AODs in year 2030, estimated based on simulations that consider future changes in emissions, are used to explore opportunities for win - win strategies built upon addressing air quality and climate change together. It is found that in 2030 the PM_2.5 levels in significant parts of Asia will increase and exacerbate health impacts; but the aerosols will have a larger masking effect on radiative forcing, due to a decrease in BC and an increase in SO₂ emissions.