Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Global warming and CO2 hotspots?

  1. Jun 14, 2008 #1
    If CO2 produced by industry is causing global warming then wouldn't there be hotspots above major industrial sites where the CO2 is most concentrated?
    And wherever in the world CO2 is washed out of the air by heavy rainfall, shouldn't there be CO2 coldspots too?
    If CO2 warming is increasing average wind speeds then are the increases in wind speeds around CO2 hotspots greater than elsewhere?
    I read on wikipedia that if the earth warms up then more water vapour is produced and this in turn leads to more heat being trapped and more water vapour forming and so on.What stops this positive feedback cycle from getting out of control? Do clouds form when the air reaches a certain humidity level and do the clouds then reflect sunlight back into space?
    Last edited: Jun 14, 2008
  2. jcsd
  3. Jun 15, 2008 #2
    Jos de Laat has done some research to local effects on industrial areas here:
    http://www.knmi.nl/~laatdej/2006joc1292.pdf [Broken]

    In the old days, the physics of water vapor was quite different:

    Priestley, C.H.B., 1966. The Limitation of Temperature by Evaporation in Hot Climates. Agricultural Meteorology, 3 (1966) 241-246.

    the logic of which is in the Clausius Clappeyron exponential relationship between temperature and evaporation for a constant relative humidity.

    For ballpark figures, from http://www.usclivar.org/Organization/Salinity_WG/workshoppresentations/Evp-salinityLisanYu.pdf [Broken] let's assume average annual evaporation of a meter per year. That's 2.74 liters (2740 g) per m2 per day or 114 g per hour is 0.032 gram per second. It takes 2500 joule to evaporate one gram of water, so for 0.032 gram that's 79 joule per second per square meter or 79 W/m2

    Now to keep relative humidity constant when increasing the ambient temperature of 15 C to 16 C, suppose a dewpoint of about 9 degrees we see here a decrease of 67% to 63%. Obviously we also have to raise the dewpoint one degree to get back to 67% Now the absolute humidity calculated here goes from 9 gram/m3 at a dewpoint of 9 degrees to 9.6 gram/m3 at a dewpoint of 10 degrees, an increase of 7%. To sustain an increase of 7% more water vapor in the atmospere it seems logical that the rate of evaporation also has to increase by 7% as well, which in turn requires 7% more energy. Hence I'd need 7% of 79 W/m2 or 5.5 W/m2 extra to maintain constant relative humidity. However the additional energy associated with doubling CO2 is about 3.4-4.0 W/m2

    So it appears that the exponential increase of energy required for evaporation exceeds the increase due the enhanced greenhouse effect, killing the positive feedback.
    Last edited by a moderator: May 3, 2017
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook