DEFINING AND ESTIMATING GLOBAL MEAN TEMPERATURE ANOMALIES

Methods used to quantify temperature changes of the earth must be asse ssed 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 da ta reuse, Distance weighting is shown to be effective for estimating g ridpoint temperature anomalies but it is not optimal for estimating re gional or global means. Gridding is shown to be more effective than us ing irregularly spaced individual temperature anomalies in the estimat ion of regional or global means. The reuse of station data in the calc ulation of averages for neighboring grids is not recommended.