Wylie’s Recent Comments

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  Water vapor forming clouds cools earth surface

  Can anyone comment on the magnitude of the cooling effect of water being evaporated at the surface of the earth (using surface heat) and then forming clouds at higher altitudes (emitting the heat high up in the troposphere)?  I would think that this cooling effect would increase as the temperature increases?  Certainly, water's heat of vaporization is very large and the amount of water being evaporated from the oceans is huge.  Couldn't this be a significant negative feedback that accelerates as the temperature rises?  WOuldn't it help to counter any heating caused by CO2 and other GHG  I haven't seen it in the GCMs, am I missing it??

     Any and all comments appreciated.

   On Water vapor is indeed a powerful greenhouse gas, but there is plenty of room for CO2 to play a role posted 1 year, 11 months ago 29 Responses

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  Questions about GHG (CO2, etc.)

  I would like to commend Coby on his very considerate tone.  There are too many insults hurled about in this debate for my preference.  Just a quick disclaimer: I am an avid proponent of energy efficiency and conservation.  Americans could use the exercise!  However, I have a few questions/thoughts:

  1) Beer's Law and Saturated CO2 absorption lines

  As I understand it, CO2 absorbs infra-red light (as does water vapor) and this is the main expected reason for the increase in temperature (although not the only one).  However, I thought that ALL light absorption followed Beer's Law of Light Absorption?  Beer's law relates the amount of light absorption (and infrared radiation as well) to the LOGARITHM of the concentration.  Therefore, and assuming this is true, the increase in the amount of light absorption arising from an increase in CO2 concentration of 40% (pre-industrial to today), would be the log of 1.4 (an increase in absorption of 14.6%).  An increase in CO2 by 100% (doubling, by 2100??)) would only increase the light absorption by ~30%.  As I understand it, those numbers ASSUME that the absorption of a given absorption line is not near saturation (i.e. very low absorption relative to 100% of the light being absorbed).  However, as I understand it, the infrared absorption lines of CO2 absorb all or nearly all the infrared light at those wavelengths in a very short distance (I have heard numbers of less than 10metres).   Can anyway explain whether or not the Global Climate Models fully incorporate Beer's law AND the saturation of infrared absorption?  How would saturated CO2 lines increase the absorption of infrared light (and thereby increase global temperatures) when the CO2 concentration increases?  I have heard objections that the infrared absorption lines are actually composed of many rotational absorptions lines that are not completely saturated when the CO2 is at high altitude (low pressure) but the pressure broadening of atmospheric pressure (close to the ground) should "merge" those lines into a large vibrational absorption band.  Is this correct?

  2) Cloud Formation as a heat transfer mechanism?

      As I understand the logic that suggests that water vapor is not a significant contributor to Global Warming (as opposed to CO2), this is because an increase in the average amount of water vapor in the air would simply result in an increase in rainfall and decrease the water vapor back to equilibrium.  However, isn't it true that the evaporation of water at sea level and the condensation of water at altitude (clouds) is a massive heat transfer mechanism from the ground to the upper troposphere?  Isn't it also true that an increase in temperature (forcing) would allow an ACCELERATION of this effect?  Therefore wouldn't there be a negative feed-back mechanism (a massive one) that would help to reduce the positive feedbacks?  Also, wouldn't this mechanism be HARD to model?  (cloud formation being a chaotic process)  Question:  Are there estimates (despite the computational difficulties) of the this cloud formation heat transfer effect and how it might change as a function of global temperature?

          Any and all thoughtful comments/observation would be gratefully received.

             On There is no proof in science, but there are mountains of evidence posted 1 year, 11 months ago 78 Responses