Black Carbon Reduces Springtime Eurasian Snow Cover Almost as Much as CO2
11 April 2009
In another study highlighting the role of black carbon particles in global warming (earlier post), a team of researchers has found that emissions from black carbon (BC) and organic matter (OM) drive springtime (March-May) melting in Eurasia nearly as much (95%) as anthropogenic CO2. The study was published in 7 April in the journal Atmospheric Chemistry and Physics. Eurasia includes the Hindu-Kush-Himalaya-Tibetan Plateau, which is the headwaters for most of the major rivers in Asia.
The study by researchers from the National Center for Atmospheric Research; University of California, Irvine; Cornell University; University of Utah; and Scripps Institute of Oceanography, University of California-San Diego, also found that 21 out of 22 climate models that contributed to the IPCC Fourth Assessment Report underpredicted the rapid observed warming in this area of .64 °C since 1979.
Carbonaceous particles can influence snow coverage by warming the atmosphere; reducing surface-incident solar energy (dimming); and reducing snow reflectance after deposition (darkening).
The researchers applied a range of models and observations to explore impacts of these processes on the springtime boreal climate, which is already susceptible to solar warming mechanisms because it has expansive snow cover and receives relatively strong insolation. Among their conclusions:
Nearly all atmospheric particles (those with visible-band single-scatter albedo less than 0.999), including all mixtures of BC and OM, increase net solar heating of the atmosphere-snow column.
Darkening caused by small concentrations of particles within snow exceeds the loss of absorbed energy from concurrent dimming, thus increasing solar heating of snowpack as well (positive net surface forcing). Over global snow, the team estimated 6-fold greater surface forcing from darkening than dimming, caused by BC+OM.
Equilibrium climate experiments suggest that fossil fuel and biofuel emissions of BC+OM induce 95% as much springtime snow cover loss over Eurasia as anthropogenic carbon dioxide, a consequence of strong snow albedo feedback and large BC+OM emissions from Asia.
Of 22 climate models contributing to the IPCC Fourth Assessment Report, 21 underpredict the rapid warming (0.64 °C decade-1) observed over springtime Eurasia since 1979. Darkening from natural and anthropogenic sources of BC and mineral dust exerts 3-fold greater forcing on spring-time snow over Eurasia (3.9 Wm-2) than North America (1.2 Wm-2). Inclusion of this forcing significantly improves simulated continental warming trends, but does not reconcile the low bias in rate of Eurasian spring snow cover decline exhibited by all models, likely because BC deposition trends are negative or near-neutral over much of Eurasia. Improved Eurasian warming may therefore relate more to darkening induced reduction in mean snow cover.
Our study finds that black carbon is especially effective at warming climate during springtime, when the Northern Hemisphere is highly reflective and transitioning into snow-free summer. By inducing early retreat of snow cover, black carbon causes (Eurasian) land areas to absorb more sunlight and warm disproportionately.—Marc Flanner, National Center for Atmospheric Research, lead author
The short atmospheric lifetime of black carbon offers the opportunity for fast mitigation. Flanner explained, “Our model studies suggest that eliminating black carbon emissions from fossil and biofuel sources would cause Eurasian springtime snow cover to recover at least a quarter of its estimated loss from pre-industrial times to the present.”
This is yet another major study revealing the major role of black carbon in the retreat of snow packs and glaciers around the world. Fortunately, we can do something about black carbon, for we know how to reduce emissions of black carbon from combustion of fossil fuels and biomass fuels.—V. Ramanathan, Scripps Institute of Oceanography at the University of California, San Diego, co-author
M. G. Flanner, C. S. Zender, P. G. Hess1, N. M. Mahowald1, T. H. Painter, V. Ramanathan, and P. J. Rasch (2009) Springtime warming and reduced snow cover from carbonaceous particles. Atmos. Chem. Phys., 9, 2481–2497
I'm waiting for the Usual Suspects to tell us why this disproves Global Warming.
Posted by: dursun | 11 April 2009 at 07:35 AM
Funny dursun, I'm waiting for them to tell us why this work is wrong, the scientists are corrupt, and any findings about anthropogenic causes to climactic variation are made by weak minds.
I suppose they can go either way on this... What's you pleasure Real? Sulley? Ex?
Posted by: Nat Pearre | 11 April 2009 at 08:35 AM
"that eliminating black carbon emissions from fossil and biofuel sources..."
This sounds like even biofuel used in a way that puts out carbon particles can cause this. I would assume this means biodiesel as well.
Posted by: SJC | 11 April 2009 at 09:55 AM
SJC - presumably, the "biofuel sources" are things like domestic wood burning.
BC and OC from diesel sources has been/will be virtually eliminated with use of DPF, which has been shown to reduce PM to background levels and even below in some cases.
Posted by: Carl | 11 April 2009 at 10:24 AM
If you google baby boomer age you will find out why concevatives dont worry about co2 and global warming as far as the us is concerned. Or china and india and and and for that matter;/
In short the most consumerist generation and the largest generation ever in the us is OLD. And the entire system is imploding as they go.
Kinda handles the problem all on its own.
Posted by: wintermane2000 | 13 April 2009 at 09:06 AM
And winter nails it. OTOH I'm of the older generation myself and I'm still worried about GW, I worry for those I'll leave behind; kids/grandkids. I guess that's what you'd call "family values" Liberal style.
Posted by: ai_vin | 13 April 2009 at 11:06 AM
This may prove to be another weapon against the coming Ice Age.. the combination of CO2 emissions falling due to the end of the oil age and the calm sun may snap us into a severe Ice Age.. all that coal in the ground may be more valued for its sooth making ability than for its energy content.
Posted by: Herm | 15 April 2009 at 02:45 AM