Scott Armstrong offered to bet Al Gore that global mean temperatures would be closer to the 2007 average over the following ten years than they would be to the IPCC projection of a 0.03C per-year increase. Gore refused the bet but, if he had taken it, he would would have found himself behind Armstrong at the end of the first four years. Armstrong's forecasting method was based on forecasting principles applied to a situation that is characterised by considerable measures of both ignorance and uncertainty, and historical evidence that apparent trends in temperatures reverse without warning. The IPCC projection is based on the beliefs of some scientists that human CO2 emissions will cause the world's climate to warm dramatically. For information on the choice of the no-change forecasting method used by Armstrong, see the Green, Armstrong, and Soon paper in the International Journal of Forecastinghere. For details of the bet to date, see theclimatebet.com.
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