Saturday, October 1, 2011

It is Just a Cartoon!

I have dug into this some more and tweaked when my estimate are a little tighter. Based on the drawing, what I have down below is a pretty accurate quick and dirty estimate. To explain the principals involved I have this post, Back to Baking Bacon Bread. For what impact that unexpected issue may have, Trenberth, Monckton and Lucia - Are They Missing the Heat? There is a lot more that really needs to be done to verify if there is really any impact, but I will try when I find time.

Some how or another, the Keihl Trenberth cartoon radiation budget has been breathed new life and is now a scientific zombie. Christopher Monckton of Brenchley, has a post on Wattsupwiththat about climate sensitivity where he derived something from the K&T cartoon. I am not sure what he was attempting to derive from the cartoon, but he was pretty adamant that he was on to something.

Well, his post was criticized by several people including Lucia at the BlackBoard. this exchange got a little heated, but what else is new. Well, the heart of the issue is whether or not you can derive the climate sensitivity of Earth from the silly cartoon energy balance. HUH?

Well, ya kinda can. If you consider that only the atmosphere responds to outgoing longwave radiation, then the amount of OLR is 26 W/m^2 after you subtract the 40 W/m^2 that gets a free pass and the 324 W/m^2 downwelling. That downwelling radiation is generated by the sum of energy absorbed by the atmosphere, so the ratio of the radiative absorbed divided by the total absorbed would be the radiative impact of the greenhouse to OLR.

26 OLR absorbed / (67 solar absorbed + 24 sensible heat absorbed + 78 latent heat absorbed + 26 radiant heat absorbed) That equals 26/195 or 0.133, 13.3% of the temperature of the atmosphere is directly due to absorbed outgoing radiation. Of course, all the other values change when radiative absorption changes, but 13.3 is pretty close to the minimum value. Since the greenhouse provides an extra 33 degrees of warmth, 13.3 % of 33 equals, 4.4 degrees is purely due to OLR. That would be the value changed with more CO2 added. One degree change in temperature is due to the overall greenhouse effect is caused by 3.7 W/m^2. I am not positive this is right, but it looks about right. If you add the 3.7 W/m^2 (26+3.7)/(195+3.7) you get 0.1495 (okay that is a few many sig digs) times 33 = 4.93 C which is (4.93-4.4)= 0.53 C minimum warming due to an increase of 3.7W/m^2 atmospheric resistance to OLR.

The latent and sensible values would definitely change with greater atmospheric resistance and the solar absorbed should a little, but is more likely to vary less, assuming it remains roughly the same, then 29.7/(67 solar +29.7 radiative) = 29.7/96.7 times 4.4, the radiative forcing portion of the 33 degree results in a maximum sensitivity of 1.35 degrees.

Considering the estimated 1.2 C climate sensitivity to no feedback is based on the 33 C and that feedbacks are supposed to kick up sensitivity, this range doesn't really say anything new, only that the K&T data was in the ballpark of reality.

Update: Just as a check, you can do the same ratio with only the surface fluxes and get 0.155K/W/m^2 or 0.60 minimum sensitivity. Not that that is particularly exciting either.

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