Friday, April 08, 2011

Black Carbon at the Top of the World (CO2 Science)

Kaspari, S.D., Schwikowski, M., Gysel, M., Flanner, M.G., Kang, S., Hou, S. and Mayewski, P.A. 2011. Recent increase in black carbon concentrations from a Mt. Everest ice core spanning 1860-2000 AD. Geophysical Research Letters 38: 10.1029/2010GL046096.

The authors write that "black carbon (BC, the absorbing component of soot) produced by the incomplete combustion of biomass, coal and diesel fuels can significantly contribute to climate change by altering the earth's radiative balance," noting that "BC is estimated to have 55% of the radiative forcing effect of CO2 (Ramanathan and Carmichael, 2008)," but that in spite of these facts, BC still remains "one of the largest sources of uncertainty in analyses of climate change."

What was done
In an effort to reduce some of this uncertainty, Kaspari et al. developed a high-resolution BC record spanning the period AD 1860-2000 from a Mt. Everest ice core extracted from the East Rongbuk glacier located on the mountain's northeast ridge on the north slope of the Himalaya, which record, in their words, "provides the first pre-industrial to present record of BC concentrations from the Himalayas."

What was learned
The seven scientists determined that "BC concentrations from 1975-2000 relative to 1860-1975 have increased approximately threefold, indicating that BC from anthropogenic sources is being transported to high elevation regions of the Himalaya." In addition, they report that "the increase in Everest BC during the 1970s is simultaneous with a rise in BC emissions as estimated from historical records of energy-related combustion in South Asia and the Middle East (Bond et al., 2007)."

What it means
Kaspari et al. say their findings suggest that "a reduction in BC emissions may be an effective means to reduce the effect of absorbing impurities on snow albedo and melt, which affects Himalayan glaciers and the availability of water resources in major Asian rivers." And since (1) Ramanathan and Carmichael (2008) note that the majority of BC emissions (60%) arise from "cooking with biofuels such as wood, dung and crop residue" and from "open biomass burning (associated with deforestation and crop residue burning)," and since (2) Venkataraman et al. (2005) note that control of BC emissions through cleaner cooking technologies alone could help in "reducing health risks to several hundred million users," it would seem more than obvious that reducing biofuel sources of BC emissions would be an extremely worthy goal.

Bond, T., Bhardwaj, E., Dong, R., Jogani, S., Jung, C., Roden, D., Streets, G. and Trautmann, N. 2007. Historical emissions of black and organic carbon aerosol from energy-related combustion, 1850-2000. Global Biogeochemical Cycles 21: 10.1029/2006GB002840.

Ramanathan, V. and Carmichael, G. 2008. Global and regional climate changes due to black carbon. Nature Geoscience 1: 221-227.

Venkataraman, C., Habib, G., Eiguren-Fernandez, A., Miguel, A.H. and Friedlander, S.K. 2005. Residential biofuels in South Asia: Carbonaceous aerosol emissions and climate impacts. Science 307: 1454-1456.

No comments: