Les Jones

Environment > About the IPCC's 90% Confidence in Human Causes for Global Warming

Via the Institute of Public Affairs*:

There are legitimate difficulties with the IPCC's 90 per cent confidence in anthropogenic warming. It is not ludicrous to question what that number means. The IPCC seems to imply that this number results from a scientific process -that it has tested a hypothesis. Indeed, the IPCC tells us its understanding is based "upon large amounts of new and more comprehensive data, more sophisticated analysis of data, improvements in understanding of processes and their simulation in models, and more extensive exploration of uncertainty ranges". If this is what the IPCC has done, it has very weak evidence. Ninety per cent is the weakest acceptable level of confidence in a hypothesis test. It is not clear from the Summary whether the IPCC has, in fact, undertaken such an analysis. It is more likely that it has neither a testable model nor data available for external researchers to replicate such a test. In other words, the IPCC's 90 per cent confidence has emerged from scientists evaluating whether they think their own work is correct.

There is an even greater problem with the analysis. The IPCC provides a breakdown of seven extreme weather events, and an assessment of human influence on those events. Only two of the individual events have a human impact of at least 66 per cent, the other five are 50-50 propositions. Somehow this all adds up to 90 per cent. Furthermore, in three of the weather events there is no underlying human attribution study -the IPCC made up that data.

* This is one of those organizations with pleasant-sounding names that I know nothing about. They are, for all I know, aligned with the devil himself.