We show that a simple model of pan evaporation ("PenPan") can be used to analyze monthly mean output from a global climate model (GCM). PenPan is based on a modified version of Penman's potential evapotranspiration equation. Very good agreement is obtained with observed annual pan evaporation for Australian sites when PenPan is forced by surface observations of radiation, wind speed, humidity and air temperature. When PenPan is forced with monthly mean output from the CSIRO GCM, the results are still satisfactory, but pan evaporation is overestimated over southern Australia, primarily due to excessive surface solar radiation simulated by the GCM. The results suggest that PenPan will be a valuable tool for reconciling observed pan-evaporation trends with climate-model simulations.