Climate and chemistry changes from 1975 to 2000 as observed and modeled in the coupled chemistry-aerosol-climate GISS ModelE Earth System Model

DESCRIPTION: Efforts to understand recent warming and other climate changes, primarily attributed to increased greenhouse gas concentrations, are confounded by concurrent changes in aerosols and short-lived gaseous species. At GISS we have developed an Earth System model framework, allowing transient model runs including gas and aerosol phase chemistry schemes fully coupled to the climate and deep ocean modules, in order to simulate aerosol as well as ozone and GHG effects on climate. We have also developed a new aerosol microphysical scheme (MATRIX), a new cloud microphysical scheme that links to MATRIX, a scheme for dependence of snow albedo on snow black carbon (BC) concentrations, and we are currently implementing secondary organic aerosols.

OUTCOMES: Examine how high-latitude aerosol reductions have affected Arctic climate, how increasing low-latitude aerosol have affected tropical clouds and climate, how the aerosol mixing state has evolved during recent decades, if our model explains the observed changes in radiation, global dimming/brightening, and how GHG and aerosol climate impacts compare, in character and magnitude. We will also participate in model and hindcast intercomparison exercises with AeroCom, AC&C and HTAP, which will provide additional datasets for comparison and evaluation of decadal predicted chemistry and climate trends.