söndag 4 september 2011

IPCC Trick of Radiative Forcing

Outgoing longwave radiation from NASA FIRST project.

The radiative effect of CO2 in the atmosphere can be read from the above picture as the reduction of the area under the above curves from the dip centered at a wave number of about 700 of width about 100. The depth of the dip ranges from 0.07 for Mid-Lat Summer to 0.02 for Sub-Arc Winter, with a mean value of about 0.05, and so the area is about 5.

The total area under the curves is about 2000 x 0.12/2 = 120. We conclude that the total effect of CO2 can be viewed as a change of radiative forcing of 5/120 or about 4%.

What could then the effect of doubled CO2 be? Well the depth of the dip is not likely to change because of saturation, only the width by some form of broadening of the absorption/emission spectrum. How much broadening?

Assuming 10% we get a radiative forcing from doubled CO2 of 0.4% of total radiative forcing of about 250 W/m2, that is about 1 W/m2.

This is to be compared with the radiative forcing by IPCC of 4 W/m2, which is a factor 4 bigger.
IPCC pulls the 4 W/m2 miraculously out of the pocket by the trivial formula dQ = 6.3 log(C/C0) with C/C0 = 2 for doubled CO2, a formula which on Climate Audit is shown to lack scientific support.

We see here yet another indication from observation of the IPCC trick of inventing a factor 5-10 to sell climate alarmism.

Note that the radiative forcing of doubled CO2 of 1 W/m2 (or the 4 W/m2 by IPCC) does not directly translate to global warming. In fact, the natural variability of the radiative forcing seems to be in the range of 5 W/m2, and so the effect of 1 W/m2 from doubled CO2 cannot be detected.

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