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Andre
Joined: 21 Jul 2007
Posts: 298
Location: Germany - The Nederlands
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 Posted: Sat Nov 24, 2007 12:34 am Post subject: Doubling CO2 and water vapor feedback |
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Post in preparation.
chap 10 of the 4AR report of the IPCC says
| Quote: | An expert assessment based on the combination of available constraints from observations (assessed in Chapter 9) and the strength of known feedbacks simulated in the models used to produce the climate change projections in this chapter indicates that the equilibrium global mean SAT warming for a doubling of atmospheric carbon dioxide (CO2), or ‘equilibrium climate sensitivity’, is likely to lie in the range 2°C to 4.5°C, with a most likely value of about 3°C. Equilibrium climate sensitivity is
very likely larger than 1.5°C. For fundamental physical reasons, as well as data limitations, values substantially higher than 4.5°C still cannot be excluded, but agreement with observations and proxy data is generally worse for those high values than for values in the 2°C to 4.5°C range. The ‘transient climate response’ (TCR, defined as the globally averaged SAT change at the time of CO2 doubling in the 1% yr–1 transient CO2 increase experiment) is better constrained than equilibrium climate sensitivity. The TCR is very likely larger than 1°C and very unlikely greater than 3°C based on climate models, in agreement with constraints from the observed surface warming. |
and also (pp759):
| Quote: | | In response to a doubling in atmospheric CO2, the specific humidity increases by approximately 20% through much of the troposphere. |
specific humidity is defined as the ratio of the mass of water vapour to the total mass of air in a given volume.
The max humidity of air depending on temperatue is:
The maximum partial pressure (saturation pressure) of water vapor in air varies with temperature of the air and water vapor mixture. A variety of empirical formulas exist for this quantity; the most used reference formula is the Goff-Gratch equation for the SVP over liquid water:
log(p)=-7.90298((373.16/T - 1) + 5.02808 log(373.16/T) etc
http://en.wikipedia.org/wiki/Water_vapor
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