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Climate Science Forum Autumn 2009 |
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CLIMATE NEWS BRIEFS |
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MORE CLIMATE NEWS BRIEFS
Record High & Low Temperatures further evidence of current warming Airborne Particles magnify impact of greenhouse gases. Arctic sensitive to climatic effects of particles in air This page . . . . . . . . . . . . At left Soot and Black Carbon: 2nd leading warming agent |
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Arctic sensitive to climatic effects of particles in air In a paper2 in Nature Geoscience early in 2009, Shindell and Faluvegi found out that particles in the atmosphere had a large role in the climate changes of the 20th century, a larger role than the IPCC was ready to admit in 2007. The authors also determined that the Arctic is especially sensitive to airborne particles and ozone pollution from the Northern Hemisphere. Over the last 30 years, when the Arctic warmed by 1.5°C, trends in airborne particle concentrations were probably responsible for two-thirds of the warming in the Arctic region. (Both the light-colored scattering particles and dark-colored sooty particles were responsible.) Decreasing numbers of light-colored particles has had a similar effect as an increasing presence of dark particles: both trends caused a warming atmosphere. Clean-air campaigns in the most developed nations combined with continuing emissions of black carbon particles from Asia have caused a rapid and large warming in the polar North. Predictions of climate changes must take into account where airborne particles and ozone pollutants are emitted, or else the predictions will likely be in error for polar and temperate zone climates.
CITATION: 2. D. Shindell and G. Faluvegi, “Climate response to regional radiative forcing during the 20th Century”, Nature Geoscience, v. 2, 294-300, March 22, 2009. |
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Warming by black carbon more widespread than before The climate consequences of releasing pollution particles into the air have been clouded by disagreements between observations and models. Observations suggested more cooling from pollution than the aerosol models predicted. Norwegian Gunnar Myhre claims to have reconciled the observational and the modeling work in a study in July of this year3. He corrected some faulty assumptions in the observational studies, and noted that optical properties of aerosol particles have been changing over the last several decades, which had not been considered in the models. Black carbon particles increased six-fold from early industrial times to today; while scattering particles increased only three-fold, Myrhe calculated. Warming by black carbon and sooty aerosols is becoming more important while cooling by the scattering aerosols is becoming less important. Thus warming from black carbon is canceling ever more of the cooling from all other aerosols (the indirect effect of particles on clouds was not considered— see paragraph 5 of the lead story for information on the indirect effect, which is larger than the direct effect). He concludes that particles now cool the global climate at a rate of -0.3 Watts per square meter, which is less cooling than the best estimate of the Intergovernmental Panel on Climate Change (IPCC) in 2007.
CITATION 3. G. Myhre (2009), “Consistency between Satellite Derived and Modeled Estimates of the Direct Aerosol Effect” – Science, v. 325, 187-190, July 10, 2009. |