HR: 09:35h
AN: A51G-06    [Abstracts]
TI: Comparative Climate Responses of Anthropogenic Greenhouse Gases, All Major Aerosol Components, Black Carbon, and Methane, Accounting for the Evolution of the Aerosol Mixing State and of Clouds/Precipitation from Multiple Aerosol Size Distributions
AU: * Jacobson, M Z
EM: jacobson@stanford.edu
AF: Stanford University, Dept. of Civil and Env. Eng. Terman M-31, Stanford, CA 94305-4020 United States
AB: Several modeling studies to date have simulated the global climate response of anthropogenic greenhouse gases and bulk (non-size-resolved) sulfate or generic aerosol particles together, but no study has examined the climate response of greenhouse gases simultaneously with all major size- and composition resolved aerosol particle components. Such a study is important for improving our understanding of the effects of anthropogenic pollutants on climate. Here, the GATOR-GCMOM model is used to study the global climate response of (a) all major greenhouse gases and size-resolved aerosol components, (b) all major greenhouse gases alone, (c) fossil-fuel soot (black carbon, primary organic matter, sulfuric acid, bisulfate, sulfate), and (d) methane. Aerosol components treated in all simulations included water, black carbon, primary organic carbon, secondary organic carbon, sulfuric acid, bisulfate, sulfate, nitrate, chloride, ammonium, sodium, hydrogen ion, soil dust, and pollen/spores. Fossil-fuel soot (FFS) was emitted into its own size distribution. All other components, including biofuel and biomass soot, sea-spray, soil dust, etc., were emitted into a second distribution (MIX). The FFS distribution grew by condensation of secondary organic matter and sulfuric acid, hydration of water, and dissolution of nitric acid, ammonia, and hydrochloric acid. It self-coagulated and heterocoagulated with the MIX distribution, which also grew by condensation, hydration, and dissolution. Treatment of separate distributions for FFS allowed FFS to evolve from an external mixture to an internal mixture. In both distributions, black carbon was treated as a core component for optical calculations. Both aerosol distributions served as CCN during explicit size-resolved cloud formation. The resulting clouds grew by coagulation and condensation, coagulated with interstitial aerosol particles, and fell to the surface as rain and snow, carrying aerosol constituents with them. Thus, cloud evolution accounted for the first and second indirect effects and the mixing state of aerosol particles. The optical properties of clouds were found by treating black carbon inclusions surrounded by a shell of water. The albedos of snow, sea ice, and water were calculated with radiative transfer solutions, assuming black carbon inclusions in the case of snow and sea ice. The simulations accounted for 3-D energy diffusion to the deep ocean and 2-D ocean circulation. Major conclusions are (a) the most important constituents of global warming, in terms of climate response, appear to be, in order, carbon dioxide, black carbon, and methane, (b) aerosol particles (all together) appear to act on top of greenhouse gases to enhance extremes in both regional cooling and regional warming, (b) the combination of important greenhouse gases and aerosol particles can explain observed major regions of historic warming and cooling, and (d) eliminating all anthropogenic aerosol emission could more than double current global warming but would have less of an effect than independently doubling carbon dioxide.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0320 Cloud physics and chemistry
DE: 3305 Climate change and variability (1616, 1635, 3309, 4215, 4513)
DE: 3311 Clouds and aerosols
DE: 3337 Global climate models (1626, 4928)
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005