New Scientist and climate change

The cover article in this week's New Scientist (10th February 2007, p6-p9), written by Fred Pearce, complains that the latest IPCC report underestimates global climate change, and that "many legitimate findings have been frozen out," because "research deemed controversial, not fully quantified or not yet incorporated into climate models was excluded."

Given that the whole raison d'etre of the IPCC reports is to present a solid, consensually agreed analysis of climate change, this seems a perverse criticism to make. The main article concludes with a quote from Venkatchalam Ramaswamy, who found that his own fears failed to make it into the IPCC summary, and complains that "Anything qualitative rather than quantitative was knocked out...By and large where there was ambiguity or controversy, it didn't make it." Again, this increases rather than decreases my confidence in the IPCC report!

There is certainly new data on, for example, the melting of ice sheets, and it is right that this data is analysed and investigated further until ice sheet melting is properly understood, but an IPCC report is not the appropriate forum for speculative debate or the extrapolation of small data sets.

My confidence in the New Scientist article is further eroded by the main diagram, which is a version of the IPCC diagram on p21 of the 'Summary for Policymakers', showing the predicted global warming under various scenarios, according to the various global climate models. New Scientist appear to have annotated their version of the diagram in a manner which is, at best, misleading. They define the error bars down the right as 'Potential error to one standard deviation'. This seems to be a mis-interpretation of the IPCC diagram, in which the shading either side of the coloured lines in the graph "denotes the plus/minus one standard deviation range of individual model annual means...The gray bars at right indicate the best estimate (solid line within each bar) and the likely range assessed for the six SRES marker scenarios. The assessment of the best estimate and likely ranges in the gray bars includes the AOGCMs in the left part of the figure, as well as results from a hierarchy of independent models and observational constraints." The error bars down the right indicate the dispersion of temperature predictions produced by the different global climate models for each scenario; they are not standard deviations produced by individual models.