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Politics : President Barack Obama -- Ignore unavailable to you. Want to Upgrade?

To: ChinuSFO who wrote (81375)	8/20/2010 3:12:04 PM
From: Wharf Rat	Respond to of 149317

"We saw the myth of Y2K" Crap, refried crap, ands refried crap sunny side up. It didn't happen cuz lots of people spent lots of time making sure it didn't happen. There are no climate theories of left and right. Political science isn't science. There are only the theories of Tyndall and Arrhenius, and they weren't Americans; they were scientists.... Carbon dioxide is a greenhouse gas – it traps heat radiation that is attempting to escape from Earth. The physics of this process was established by the Irish physicist John Tyndall (1820 – 1891) and the effect was calculated by Swedish chemist Svante Arrhenius (1859 – 1927). The basic argument (that is, that greenhouse gases keep the Earth comfortably warm) has never been challenged, and it follows that an increase in carbon dioxide in the atmosphere undoubtedly produces a rise in temperature at ground level. More information on the greenhouse effect. Given this background, we next need to ask: How much of the observed warming in this last century can be ascribed to the observed loading of the atmosphere with greenhouse gases by human activities? Svante Arrhenius (Courtesy: www.nobel.se) First, we turn to the reconstruction of the rise of carbon dioxide since the time of James Watt. The early part of the series is derived from extracting air in polar ice, and measuring its carbon dioxide content. The later part is based on the measurements of Charles D. Keeling, since 1957, on Mauna Loa. The overall rise is from just below 280 ppm (the “pre-industrial” value) to the present values above 360 ppm, an increase of a factor of 1.3. The logarithm of 1.3 is 0.11, that of 2 is 0.30. Thus, we are a little more than one third of the way to a doubling of carbon dioxide, on a log scale. If doubling of carbon dioxide produces a temperature rise of between 1.5 and 5 degrees Celsius (as found in numerical experiments using climate models), we should see a warming of between 0.5 and 1.7 degrees Celsius. We do see the lower number of this range, but this does not prove that the rise upon doubling of carbon dioxide is in fact 1.5 degrees. The reason is that we are in a “transient”, that is, the change is too fast to allow equilibrium to establish itself. Graph showing rise of CO2, from measurements in ice cores (Siple, Antarctica) and measurements from Mauna Loa, Hawaii (Keeling curve) since James Watt, inventor of the steam engine. (Pre-1990 data in: B. Moore & D. Schimel, 1992. Trace Gases and the Biosphere. UCAR, Boulder CO) In fact, the answer is not known with a high degree of certainty, not only because of the lack-of-equlibrium problem (which involves uptake of heat by the ocean), but also because of additional complexities arising from air pollution, trace gases other than carbon dioxide, possible changes in the brightness of the Sun, and effects from volcanic activity. Thus, in answer to the above question: Estimates vary from “little” to “much” to “most”, with the latter answer being the more credible one. One way to obtain a quick estimate answer is by doing some simple calculations, based on the work of Svante Arrhenius, assuming a 2 degree Celsius rise in temperature per doubling of carbon dioxide (Arrhenius proposed a somewhat greater effect, neglecting compensating factors). The result is the graph below, showing that CO2 forcing can explain the temperature rise. That said, there may also be a role for the Sun in modifying the temperature rise driven by greenhouse gases. The minor drops in temperature right after 1900 and after 1960 coincide with reduced solar activity. To be sure, while this simple calculation may be enough to explain the observations, it is not a mathematical proof that the warming that has occurred since the days of James Watt is entirely due to human activity. It merely represents the simplest possible explanation. earthguide.ucsd.edu