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Dependence of climate forcing and response on the altitude of black carbon aerosols

Ban-Weiss, George A and Cao, Long and Bala, G and Caldeira, Ken (2012) Dependence of climate forcing and response on the altitude of black carbon aerosols. In: Climate Dynamics, 38 (5-6). pp. 897-911.

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Abstract

Black carbon aerosols absorb solar radiation and decrease planetary albedo, and thus can contribute to climate warming. In this paper, the dependence of equilibrium climate response on the altitude of black carbon is explored using an atmospheric general circulation model coupled to a mixed layer ocean model. The simulations model aerosol direct and semi-direct effects, but not indirect effects. Aerosol concentrations are prescribed and not interactive. It is shown that climate response of black carbon is highly dependent on the altitude of the aerosol. As the altitude of black carbon increases, surface temperatures decrease; black carbon near the surface causes surface warming, whereas black carbon near the tropopause and in the stratosphere causes surface cooling. This cooling occurs despite increasing planetary absorption of sunlight (i.e. decreasing planetary albedo). We find that the trend in surface air temperature response versus the altitude of black carbon is consistent with our calculations of radiative forcing after the troposphere, stratosphere, and land surface have undergone rapid adjustment, calculated as ``regressed'' radiative forcing. The variation in climate response from black carbon at different altitudes occurs largely from different fast climate responses; temperature dependent feedbacks are not statistically distinguishable. Impacts of black carbon at various altitudes on the hydrological cycle are also discussed; black carbon in the lowest atmospheric layer increases precipitation despite reductions in solar radiation reaching the surface, whereas black carbon at higher altitudes decreases precipitation.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to Springer.
Keywords: Black carbon;Aerosol;Soot;Climate change;Global warming; Altitude;Fast response;Climate sensitivity;Feedback parameter
Department/Centre: Division of Earth and Environmental Sciences > Divecha Centre for Climate Change
Division of Mechanical Sciences > Centre for Atmospheric & Oceanic Sciences
Date Deposited: 12 May 2012 10:28
Last Modified: 12 May 2012 10:28
URI: http://eprints.iisc.ernet.in/id/eprint/44398

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