SOIL CARBON AND CLIMATE CHANGE NEWS
From Kansas State University's:
Consortium for Agricultural Soils Mitigation of Greenhouse Gases (CASMGS)
http://soilcarboncenter.k-state.edu
Charles W. Rice, K-State Department of Agronomy, National CASMGS Director
(785) 532-7217 cwrice@ksu.edu
Scott Staggenborg, K-State Department of Agronomy (785) 532-7214 sstaggen@ksu.edu
Steve Watson, CASMGS Communications (785) 532-7105 swatson@ksu.edu
Atmospheric CO2: Principal Controller
Of Earth’s Temperature
Ample physical evidence shows that carbon dioxide (CO2) is the single most important climate-relevant greenhouse gas in Earth’s atmosphere, according to a paper in the Oct.15, 2010 issue of Science. The authors of the paper are scientists from the NASA Goddard Institute for Space Studies.
Excerpts from the paper:
The Sun is the source of energy that heats Earth. Besides direct solar heating of the ground, there is also indirect longwave (LW) warming arising from the thermal radiation that is emitted by the ground, then absorbed locally within the atmosphere, from which it is re-emitted in both upward and downward directions, further heating the ground and maintaining the temperature gradient in the atmosphere. This radiative interaction is the greenhouse effect, which was first discovered by Joseph Fourier in 1824, experimentally verified by John Tyndall in 1863, and quantified by Svante Arrhenius in 1896. These studies established long ago that water vapor and CO2 are indeed the principal terrestrial GHGs. Now, further consideration shows that CO2 is the one that controls climate change.
CO2 is a well-mixed gas that does not condense or precipitate from the atmosphere. Water vapor and clouds, on the other hand, are highly active components of the climate system that respond rapidly to changes in temperature and air pressure by evaporating, condensing, and precipitating. This identifies water vapor and clouds as the fast feedback processes in the climate system.
In round numbers, water vapor accounts for about 50% of Earth’s greenhouse effect, with clouds contributing 25%, CO2 20%, and the minor GHGs and aerosols accounting for the remaining 5%. Because CO2, O3, N2O, CH4, and chlorofluorocarbons (CFCs) do not condense and precipitate, noncondensing GHGs constitute the key 25% of the radiative forcing that supports and sustains the entire terrestrial greenhouse effect, the remaining 75% coming as fast feedback contributions from water vapor and clouds.
Various atmospheric components differ in their contributions to the greenhouse effect, some through feedbacks and some through forcings. Without carbon dioxide and other non-condensing greenhouse gases, water vapor and clouds would be unable to provide the feedback mechanisms that amplify the greenhouse effect. (Source: NASA GISS)
The complete article can be found at:
http://www.sciencemag.org/cgi/content/full/330/6002/356
-- Steve Watson, CASMGS Communications