[email protected] wrote:
>> I haven't followed all of the calculation in detail, but this is wrong.
>> It doesn't matter what the feedbacks are, 2xCO2 is still only 4W/m^2.
>> What the feedbacks do is change the amount by which the outgoing
>> radiation changes as the planet warms.
>
> I am not sure what Michael means with "feedbacks included" on
> reflection.
>
> I am also not entirely sure what you are saying here, but I think it's
> probably that the greenhouse gas water vapour is temperature dependent
> and if all of the 4 W per m2 from CO2 go towards melting ice, then
> none is available for increasing Earth's temperature and therefore the
> concentration of water vapour stays contstant.
Perhaps my previous message was not as clear as it could have been. On
an initial doubling of CO2, the imbalance is 4W/m^2 before there are any
other changes. As the atmosphere warms, the water vapour increases but
the radiative imbalance *decreases* anyway, because the warmer
atmosphere is closer to radiative equilibrium (ie outgoing LW radiation
increases). A high sensitivity just means that the disequilibrium
decreases slowly as the temp increases. If the disequilibrium actually
increased with warming, the system would be unstable.
James
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