Michael Crichton’s State of Confusion

Dr Hansen is further quoted (a little out-of-context) saying: “The forcings that drive long term climate change are not known with an accuracy sufficient to define future climate change”. Given the discussion above it is clear that without good estimates of the actual forcings, the differences in the model projections can be large. It is widely accepted that exact prediction of what will happen to climate in 50 or 100 years is impossible. Much of the future is of course unknowable. A new energy source could replace fossil fuels, governments could control emissions, or maybe a series of huge volcanoes will erupt. Therefore it is much more sensible to ask, what would climate be like if you doubled CO2? or if this or that scenario occurred. These are much better defined questions. Hansen’s quote is often taken to imply that models are so unreliable they are useless in helping assess the issue. In fact it is the opposite – Hansen is actually claiming that the uncertainty in models (for instance, in the climate sensitivity) is now less than the uncertainty in the emissions scenarios (i.e. it is the uncertainty in the forcings, that drives the uncertainty in the projections).

Continuing to p315, it is claimed that “in the 1970′s all the climate scientists believed an ice age was coming” (and, as described on p563, the MIT academic apparently still thinks so). However, this is not an accurate statement and William Connolley’s pages on the subject are an illuminating read for those wanting more details.

Another issue that often comes up in discussion about the surface temperature record is the impact of the Urban Heat Island Effect (UHIE), and here it appears on p370. It is undisputed that the centres of cities such as New York are significantly warmer than the surrounding countryside. This issue has been extensively studied and is corrected for in all analyses of the global temperature trends. To see whether there might still be a residual effect in the corrected data, a recent paper (Parker, Nature, 2004) looked at the differences in the trends if you looked separately at windy and not-so-windy conditions. Wind is known to diminish the impact of urban heating, and so the trends on windy days should be less than trends on still days if this was important. The trends actually end up almost exactly the same. Other validating data for the corrected surface temperature record comes from the oceans, which have also been warming in recent decades. Even Richard Lindzen , normally an arch-skeptic on these issues, stated that “ocean temperature increases present some support for the surface temperature record” Lindzen (2002). Another demonstration that the corrections are sufficient is that over the continental US, where many cities have a clear urban heating signal, the mean of the corrected data is actually rather flat (p88) – i.e. none of the strong urban biases in the US has made it into the regional or indeed global mean.

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