How do anthropogenic aerosol trends change arctic and global climate in CCSM4 over the 20th century?
Abstract
Since the Clean Air Act began in 1972, global mean sulfate aerosol concentration has been decreasing rapidly, while black carbon concentration has been increasing continuously. What impacts would these aerosol concentration trends impose on the arctic and global climate? In this study, we use atmospheric aerosol single-forcing simulations of the Community Climate System Model version 4 (CCSM4), which has fully coupled atmosphere, ocean, land and sea ice components. The single forcing experiments were carried out by prescribing the time- and space-evolving concentrations of sulfate and black carbon, respectively. The aerosol concentrations were derived from an earlier version of the atmosphere component model run with interactive chemistry and observational-based estimates of reactive-gas emissions. All other forcings were kept fixed at 1850 levels, including surface deposition of black carbon on snow and sea ice. In an ensemble mean of 9 integrations, sulfate aerosols alone could produce ~0.3 K/Decade warming in surface air temperature over the Eurasian arctic from 1975 to 2005 through direct radiative forcing. The increased atmospheric concentration of black carbon reduces the surface air temperature in the arctic, and produces up to 0.5 K/Decade cooling in the Eurasian arctic. In agreement with previous studies, the Arctic cooling from increased atmospheric black carbon concentration is mainly caused by a reduction in atmospheric northward heat transport.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFMGC23A0904Y
- Keywords:
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- 0305 ATMOSPHERIC COMPOSITION AND STRUCTURE Aerosols and particles;
- 1600 GLOBAL CHANGE