July 2014

Understanding Soot’s Effect on Snow Reflectivity

Model comparison evaluates black carbon levels and impacts.

Click to enlarge photo. Enlarge Photo

Image from Lee et al. “Evaluation of preindustrial to present-day black carbon and its albedo forcing from Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP).” Atmos. Chem. Phys. 13, 2607–2634 (2013).

Global distribution of black carbon in 2000 among eight different models, whose results diverged the most in polar regions.

The Science

When deposited on ice or snow, the black carbon (i.e., soot) emitted from wood burning and combustion of fossil fuels such as diesel or coal reduces surface brightness or albedo, enhancing melting. Once melted, a much darker surface is exposed, accelerating a tendency toward climate warming. However, the magnitude of this effect is not well known.

The Impact

A clearer understanding of how black carbon affects the reflectivity (albedo) of snow will improve the ability of climate models to predict snow melting and future climate warming.

Summary

As part of the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP), Department of Energy scientists at Pacific Northwest National Laboratory compared historical black carbon aerosols simulated by eight ACCMIP models with observations including ice core records, long-term surface mass concentrations, and recent measurements of Arctic black carbon snowpack. The global black carbon burden from preindustrial to present-day levels increased 2.5 to 3 times with little variation among models, roughly matching the 2.5-fold increase in total black carbon emissions estimated during the same period. However, the models diverged substantially at both Northern and Southern Hemispheric high-latitude regions for black carbon burden and at Southern Hemispheric high-latitude regions for deposition fluxes, thus reflecting differences in poleward transport among models.

Contact

Y.H. Lee
NASA Goddard Institute for Space Studies and Columbia Earth Institute, New York, NY
yunha.lee@nasa.gov

Funding

Funding, in part, comes from the DOE Office of Science Biological and Environmental Research (BER) program and BER’s Atmospheric Radiation Measurement (ARM) Climate Research Facility.

Publications

Lee, Y.H., et al. “Evaluation of preindustrial to present-day black carbon and its albedo forcing from Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP ).” Atmos. Chem. Phys. 13, 2607–2634 (2013). [DOI: 10.5194/acp-13-2607-2013].

Highlight Categories

Program: BER, CESD

Performer/Facility: University, DOE Laboratory, SC User Facilities, BER User Facilities, ARM

Last modified: 8/1/2014 1:20:04 PM