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Global Warming

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The controversy over global warming (is it happening and what is causing it if it is) is rather strange. Nobody disagrees that simple models of the atmosphere, solar heating, … all show that other-things being equal if there are more greenhouse gasses in the atmosphere the mean surface temperature will be higher than otherwise. There are several problems with this; that of other-things being equal and the validity of the modelling and no doubt others that I can’t think of at present. But it is clear that we should start with the hypothesis that increasing green house gasses increases mean surface temperatures. Our task is now to fill in the gaps, improve modelling account for the “other-things”, which is what climate science seeks to do.

It is not possible to prove Anthropic Global Warming simply by displaying a (mean global surface) temperature against time plot because climate is not a fixed thing, it changes due to a number of other causes. To be more precise no “hockey stick” plot on its own proves anything. The plot that we need to see is the plot showing the difference in temperature between what would have been observed without human generated greenhouse gasses and actual observed temperatures against time. This is a difficult job, we need to establish a long-ish time series of global average surface temperature which extends back before satellite data became available, preferably to before industrialisation or longer. Parts of this record must be reconstructed from ground station records which may be contaminated with heat-island effects from growing cities or just relocation of the stations etc. The time series of temperatures in the absence of anthropic green house gasses has to be produced by climate models, and as we all know such models are always incomplete and may in parts have poor validation status.

Now climate scientists tell us that the plots do in fact show global warming over what would otherwise have occurred (of course subject to caveats about the noise, modelling fidelity, etc). Other things being equal we should believe them since it would be the opposite finding that would be extraordinary and require further investigation.


Written by CaptainBlack

March 8, 2010 at 08:19

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