Steve McIntyre’s recent Ohio State University presentation is now available online. This is an excellent summary of the ‘Hockey Stick’ debate and the climate debate in general, which extends to 45 pages (including references).
The presentation concludes:
So where does that leave us?
In my opinion, there are serious and probably fatal problems with the main proxies used as supposed evidence against a warm MWP – the Graybill strip bark chronologies, Briffa’s adjustment to the Tornetrask series, the inconsistency between Briffa’s Yamal substitution and the updated Polar Urals series and so on. For every proxy that supposedly shows a MWP cooler than the present, there seems to be one that is just as good or better evidencing the opposite. For the California and Urals proxies so fundamental to the Hockey Stick, the ecological evidence is further evidence against the Graybill and Briffa chronologies being interpretable as temperature proxies.
The selection of proxies in studies displayed by IPCC seems to me to be biased against proxies with a warm MWP. IPCC itself does not carry out any independent due diligence of the type that might be expected in a prospectus. Further, in 2007, as in 2001, the authors involved in preparing the paleoclimate section were active parties in controversies and, in the end, IPCC Fourth Assessment Report strongly reflects their partisan point of view.
Is there a wider lesson here for engineers? We are often told that the “Science is settled”. But engineers, of all people, know that, even if the “science is settled”, the engineering work may have just begun. One would hardly derive the parameters for a chemical process from an article in Nature without an engineering feasibility study.
The most critical question in climate is the estimation of a parameter – is the sensitivity of climate to doubled CO2 1.5, 2.5 or 3.5 deg C? Or could it be 6 deg C or 0.6 deg C?
In some ways, the estimation of such parameters through the development of complicated computer models is reminiscent of activities carried out by engineers. One important difference is that climate scientists typically report their results in highly summary form in journals like Nature, rather than in the 1000-page or 2000-page engineering studies that an aerospace engineering enterprise would produce.
Viewed from this perspective, a remarkable aspect of the climate debate has been the seeming inability of the climate science community to narrow confidence intervals on this estimate. In 1979, the Charney Report (National Research Council 1979) estimated the impact at 3 deg C with a 1.5 degree range either way. In 2007, IPCC AR4 estimates are virtually unchanged. With all the improvements in scientific knowledge and all the efforts of climate scientists over the years, why has the improvement of these confidence intervals proved so resistant? I don’t know, but it’s worth thinking about.

Jennifer Marohasy BSc PhD has worked in industry and government. She is currently researching a novel technique for long-range weather forecasting funded by the B. Macfie Family Foundation.