Arthur Smith's comment in reply to E. Patrick Mosman, on the

More on Why White House Blocked CO2 Curbs

thread of the New York Times' Dot Earth blog (by Andrew Revkin):

#186. July 21st, 2008, 11:25 a.m.

E. Patrick Mosman (#182) raises the “signature” claim that was also highlighted in Monckton’s APS FPS article cited so gleefully above. But I am not aware of anybody from the scientific consensus side stating that this “hot spot” is in any way a “fingerprint” -- maybe it’s expected from the models, but it’s not something central to the greenhouse effect in itself.

What *is* a signature of greenhouse gas warming, and what can be seen easily from the images in Monckton’s article, is differential heating and cooling between the surface and the stratosphere. Stratospheric cooling in particular is a key signature of greenhouse gas warming, because it is the first thing that happens when the radiative fluxes are out of balance: the increased greenhouse gas concentration results in increased emission (just as it results in increased absorption) and those layers closest to outer space must necessarily cool at least until things eventually return to radiative balance (the actual spectral dependence results in cooling even after the return to a steady state).

You will note in Monckton’s Figure 4, none of the other posited causes of warming (changing solar intensity, volcanoes, anthropogenic ozone or aerosols) results in any cooling of the top of the atmosphere: most warm the atmosphere uniformly. Only increased GHGs cool the stratosphere. And then, look at his Figure 6 showing the observations -- lo and behold, the stratosphere has cooled down!

Of course Mosman’s other points should be familiar to people on this blog as already having been repeatedly shot down (I recommend http://www.skepticalscience.com/ for each of those), but I thought it would be interesting to highlight the “fingerprint” issue as a new piece of misinformation not on the usual delayer checklist (perhaps it will be soon though, with Monckton gaining publicity!).

— Posted by Arthur Smith