Sunday, December 27, 2009
The "Saturation Myth"
William Lynch wrote in the News and Observer on Dec.17 that more than 300 ppm CO2 in the atmosphere would absorb all of the infrared re-radiation coming up from the Earth's surface. According to that logic, further increases in CO2 would not cause any more global warming. Unfortunately, Dr. Lynch repeated a very old mistake, first made around 1900. But Dr. Lynch has good company, as Knut Ångström was the first scientist to make this mistake.
Increasing carbon dioxide will continue to increase global warming. Satellite measurements show that as atmospheric CO2 increased between 1970 and 1997, from 320 to 365 ppm, there was greater absorption of the infrared wavelengths absorbed by the CO2 (see http://www.nature.com/nature/journal/v410/n6826/abs/410355a0.html). Two other articles extended those findings through 2006 when CO2 was up to 380 ppm. And the satellite observations indicate there is still plenty of infrared yet to be absorbed, so further increases in CO2 will cause further warming.
Ray Pierrehumbert and Spencer Weart give a more complete explanation and history at http://www.realclimate.org/index.php/archives/2007/06/a-saturated-gassy-argument-part-ii/. There are somewhat complicated reasons why the saturation hypothesis is a myth. The most important one may be that CO2 absorbs infrared at several wavelengths, and the energy at many of those wavelengths is not yet completely absorbed by CO2, and will not be even at double, triple, or four times the pre-industrial concentration of 280 ppm!
Is there some aspect of global warming that these climate scientists have not thought of already? Climate science, it's their passion AND their business!
We ignore history at our peril.