[ RadSafe ] Keeping an open mind Are we keeping an open mind?

[Bernard L. Cohen]

  There is a very important difference between the way CO2 and H2O 
relate to global warming. The H2O in our atmosphere is simply related to 
the temperature; this is because there is so much ocean water, that its 
vapor pressure is the determining factor, and that depends only on 
temperature.
     As described in standard Geology textbooks, the situation of CO2 is 
much more complex. It is related to the carbon available, but 99+ 
percent of the Earth's carbon is in carbonate rocks, mostly calcium 
carbonate. Increased temperature accelerates weathering of calcium 
silicate rocks (silicate rocks are much more common than carbonate 
rocks) which releases calcium into the oceans where microscopic sea 
animals combine it with dissolved CO2 to produce (eventually) calcium 
carbonate rocks (e.g. the white cliffs of Dover). This depletes the CO2 
in the oceans which causes more CO2 from the atmosphere to dissolve in 
the oceans, reducing the atmospheric CO2, and thus cooling the Earth. 
Overall, then, there is a temperature regulating process -- increased 
temperature leads to cooling (and vice versa) which is a stabilizing 
feedback on a geologic time scale.  While the amount of carbon in fossil 
fuels is very much less than that in carbonate rocks, releasing all of 
the former suddenly (on a geologic time scale) could easily disturb that 
balance.

On 10/20/2010 10:45 AM, Emer, Dudley wrote:
> Sorry Brent, I didn't see that message.   My only point was that the
> atmospheric composition of Venus and Earth is dramatically different
> when looking at CO2 / H2O ratios. The predominant warming mechanism of
> Venus is CO2 while Earth's is H20.

-- 
Bernard L. Cohen
Physics Dept., University of Pittsburgh
Pittsburgh, PA 15260
Tel: (412)624-9245  Fax: (412)624-9163
e-mail: blc at pitt.edu  web site: http://www.phyast.pitt.edu/~blc