DEFINING AND ESTIMATING GLOBAL MEAN TEMPERATURE ANOMALIES

Methods used to quantify temperature changes of the earth must be assessed relative to an appropriate definition of global mean temperature. In this paper, global mean temperature is defined and the adequacy of using weighted average anomalies to estimate a global mean anomaly is investigated, with special emphasis on the effects of gridding and data reuse, Distance weighting is shown to be effective for estimating gridpoint temperature anomalies but it is not optimal for estimating regional or global means. Gridding is shown to be more effective than using irregularly spaced individual temperature anomalies in the estimation of regional or global means. The reuse of station data in the calculation of averages for neighboring grids is not recommended.