For some time Monckton has been making claims along the lines of:For some time Monckton has been making claims along the lines of:
“In particular, the models predict that if and only if Man is the cause of warming, the tropical upper air, six miles above the ground, should warm up to thrice as fast as the surface”
And suggesting that since this hasn’t been directly measured by satellites or weather balloons, Man can’t be causing warming. Let’s detour one at a time to the graphs he uses, with the first one showing computer models' expected temperature changes across the atmosphere from 1890 to 1990 from greenhouse gases alone. Blue/purple meaning cooling since 1890 and yellow/red meaning warming:
The y-axis is atmospheric height and the x-axis is latitude – left is North and right South.
The middle of the horizontal axis is the equator and the big red circles show that the lower atmosphere around there (orange, lower down) is expected to warm less strongly than the upper atmosphere (red, higher up at ~200 hPa on the y axis). This isn't a greenhouse only jig, here's the modelled change in temperatures caused by the Sun since 1890:
The big red circles show, once again, we expect the tropical upper air to warm faster from solar heating too: Monckton said that this was a human-only jig but his graphs say that it isn't.
This ‘hot spot’ happens because any warming means more evaporation, which cools the surface. The vapour then travels up the atmosphere and condenses higher up, releasing latent heat and boosting warming there (Soden & Held, 2006). The 'hot spot' is the signal that the surface is cooling by sweating like we expect it to.
Temperatures high up are rising and changing wind patterns suggest that the tropical upper air is warming much faster than the surface (Allen & Sherwood, 2008), but temperature sensors have only found a similar rate of warming to the surface. Scientists know there are problems with measurements at this height (e.g. Randel and Wu, 2006), so can't be sure that the temperature measurements are good enough here to rule out the 'hot spot'.
However, if it isn't there then Monckton is pointing out that we're mainly missing a cooling feedback. He realises that it's a cooling effect because he also says;
"the models predict that every Celsius degree of warming should increase evaporation from the Earth’s surface by 1-3%, but the observed increase is more like 6%. From this it is simple to calculate that the IPCC has overestimated fourfold the amount of warming we can expect from adding greenhouse gases to the atmosphere."
Which dodges an important point: if this is causing surface cooling by evaporation it must cause warming higher up when it condenses. Either there is more evaporative cooling and a hot spot higher up or there isn’t and the hot spot doesn't exist.
Monckton implies that the hot spot is a human only response (it isn't) and claims it isn't there (it might be) before saying that in fact we should have a much bigger one than most models predict. Confused?
Posted by MarkR on Thursday, 24 February, 2011
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