Friday, 22 March 2013

Why Have Global Temperatures Remained Constant For 15 Years Despite Increasing Greenhouse Gas Emissions?

"The IPCC put the transition between natural and anthropogenic influence as 1960-1980. Since the global temperature started to rise about 1980, and continued to 1997, this makes the lack of variability seen in global temperatures since 1997 highly unusual."
David Whitehouse in his report (pdf).

That is really the key point here; it is illegitimate to infer from comparison with previous standstills in global temperature (e.g. 1940-1980) that the current standstill (1997-2012) is not inconsistent with the anthropogenic global warming hypothesis and that is because the period of primarily anthropogenic influence on global temperatures is supposed to begin around 1980 according to the IPCC itself.

The current ten to fifteen year temperature standstill is visible across several datasets, including the new, combined land and sea dataset "HADCRUT4", the land-only "BEST" dataset, and the lakes and reservoirs dataset by Schneider et al.

 (All images taken from Whitehouse's pdf report).

If anthropogenic greenhouse gas emissions were the primary driver of global temperatures, then an unbiased observer would have expected temperatures to have shown some statistically significant increase during the past fifteen years - as indeed were predicted by climate models referenced by the IPCC in their draft 5th Assessment Report...

Yet this statistically significant increase in temperatures hasn't happened. Once that is taken into account then, it would seem reasonable to suppose that there are other mechanisms governing global temperature trends which override the influence of greenhouse gases over water vapour convection.

That would be a very difficult thing to admit however, simply because so much money and so much "psychological investment" is at stake. Too many people have staked their professional lives and their reputations upon an hypothesis which is looking more and more every year like a falsified hypothesis.



I should add that one objection to the skeptical implications of the temperature standstill is the argument that since climatic patterns must - by convention - be observed over a time interval of thirty years, another fifteen years of standstill would be required to falsify the anthropogenic global warming hypothesis. However, that stipulation cuts both ways because - like the standstill - there has only been fifteen years of statistically significant global warming during the period since 1980 when anthropogenic greenhouse gas emissions were supposed to be the primary driver of climate change.

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