Aerosol climate effects and air quality impacts from 1980 to 2030

We investigate aerosol effects on climate for 1980, 1995 (meant to reflect present day) and 2030 using the NASA Goddard Institute for Space Studies climate model coupled to an on-line aerosol source and transport model with interactive oxidant and aerosol chemistry. Aerosols simulated include sulfates, organic matter (OM), black carbon (BC), sea-salt and dust and, additionally, the amount of tropospheric ozone is calculated, allowing us to estimate both changes to air quality and climate for different time periods and emission amounts. We include both the direct aerosol effect and indirect aerosol effects for liquid-phase clouds. Future changes for the 2030 A1B scenario are examined, focusing on the Arctic and Asia, since changes are pronounced in these regions. Our results for the different time periods include both emission changes and physical climate changes. We find that the aerosol indirect effect (AIE) has a large impact on photochemical processing, decreasing ozone amount and ozone forcing, especially for the future (2030–1995). Ozone forcings increase from 0 to 0.12 W m−2 and the total aerosol forcing decreases from −0.10 to −0.94 W m−2 (AIE decreases from −0.13 to −0.68 W m−2 ) for 1995–1980 versus 2030–1995. Over the Arctic we find that compared to ozone and the direct aerosol effect, the AIE contributes the most to net radiative flux changes. The AIE, calculated for 1995–1980, is positive (1.0 W m−2 ), but the magnitude decreases (−0.3 W m−2 ) considerably for the future scenario. Over Asia, we evaluate the role of biofuel- and transportation-based emissions (for BC and OM) via a scenario (2030A) that includes a projected increase (factor of 2) in biofuel- and transport-based emissions for 2030 A1B over Asia. Projected changes from present day due to the 2030A emissions versus 2030 A1B are a factor of 4 decrease in summertime precipitation in Asia. Our results are sensitive to emissions used. Uncertainty in present-day emissions suggests that future climate projections warrant particular scrutiny.