SOME MODEL-BASED INFERENCE ABOUT GLOBAL WARMING

The magnitude of the response of global temperature to changes in atmospheric composition depends on a parameter called temperature sensitivity. The value of this parameter is unknown. When temperature sensitivity is estimated by fitting the response of a climate model forced by historical changes in atmospheric composition to the historical trend in global temperature, the estimate is rather low. It has been suggested that this may be due to the suppression of warming by sulphate aerosols, an effect that is difficult to incorporate into model experiments. This paper presents an approach to estimating temperature sensitivity based on historical temperature variability, rather than trend, which circumvents this problem. The results are in close agreement with those based on fitting the trend.