03/05/2013
Black Carbon Effects on Ice Albedo Forcing
Summary
When black carbon (BC) or soot, emitted during combustion of fossil fuels such as diesel or coal or from wood burning, is deposited on ice or snow, it reduces surface brightness or albedo, enhancing melting. Once melted, a much darker surface is exposed, accelerating a tendency toward climate warming. However, the size of this effect is not well known. Research in the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP), including by U.S. Department of Energy scientists at Pacific Northwest National
Laboratory, evaluated the historical BC aerosols simulated by eight ACCMIP models against ice core records, long-term surface mass concentration observations, and recent Arctic BC snowpack measurements. The global BC burden from pre-industrial to the present day increased by 2.5–3 times with little variation among models, roughly matching the 2.5-fold increase in total BC emissions estimated during the same period. The models had a large divergence at both Northern Hemisphere and Southern Hemisphere high latitude regions for BC burden and at Southern Hemispheric high latitude regions for deposition fluxes reflecting differences in poleward transport among models. Clearly, substantial work remains to refine model simulations of BC and its removal and deposition on snow before a clear understanding of its snow-albedo climate effects will be possible.
References
Lee, Y.H., J.-F. Lamarque, M. G. Flanner, C. Jiao, D. T. Shindell, T. Berntsen, M. M. Bisiaux, J. Cao, W. J.
Collins, M. Curran, R. Edwards, G. Faluvegi, S. Ghan, L. W. Horowitz, J. R. McConnell, J. Ming, G. Myhre, T. Nagashima, V. Naik, S. T. Rumbold, R. B. Skeie, K. Sudo, T. Takemura, F. Thevenon, B. Xu, and J.-H. Yoon. 2013. “Evaluation of Pre-Industrial to Present-Day Black Carbon Aerosols and Its Albedo
Forcing from Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP),” Atmospheric Chemistry and Physics 13, 2607–34. DOI: 10.5194/acp-13-2607-2013.