Global and Regional Aerosol Direct Radiative Forcing Sensitivities to U.S. Emissions

FARHAN AKHTAR (1), Rob Pinder (1), Daven Henze (2), Robert Spurr (3)

(1) U.S. Environmental Protection Agency, (2) University of Colorado, Boulder, (3) RT SOLUTIONS Inc.

     Abstract Number: 644
     Last modified: May 14, 2010

Abstract
Given the daunting challenge of transforming the global energy system away from carbon-intensive fuels and the long time periods needed to alter key greenhouse gas concentrations, alternative management of emissions of short-lived climate forcers is needed to mitigate the prospect of immediate and rapid climate change. However, the management of short-lived climate forcers is complicated due to their mixed effects on radiative transfer. For example, the direct warming effect of black carbon particles is offset by light-scattering aerosols, such as organic carbon and sulfate. Few sources emit these species in isolation, and instead, produce a mixture of light-absorbing and light-scattering aerosols. We use the GEOS-Chem/LIDORT adjoint model to understand the net impact of emissions from specific source sectors on the atmospheric radiative energy balance. We model the change in radiative forcing due to emissions of black carbon, organic carbon, and SO$_2 from fossil fuel based power production, biomass burning, and mobile-source diesel sources under spring, summer, fall, and winter conditions. In addition, since these short-lived particulates are not globally dispersed, we investigate how the regional distribution of these sources can impact radiative transfer in critically sensitive areas, such as the Arctic. We compare the impacts of each source sector on radiative forcing in the Arctic and globally-averaged. Understanding how these emission sources impact global and regional radiative forcing can inform the emissions management process to mitigate the rate of climate change while achieving goals set forth by clean air and other environmental protection laws.