• simulation;
  • coupled model;
  • multi-millenial analysis;
  • climatic outliers


A 10 000-year simulation for ‘present’ climate has been generated with the CSIRO Mark 2 coupled climatic model. In this paper the model output has been analysed to produce a climatology of climatic outliers and to assess the role of such outliers in climatic variability. An assessment of the frequency of occurrence of outliers, compared with the statistical expectation from a Gaussian distribution, indicates that over most of the globe the surface temperature conforms to this distribution, but this is not the case for rainfall. Among the issues considered are the spatial occurrence rates over the globe of normalised climatic anomalies of various magnitudes, the temporal variability of outliers, the seasonal variability for a given outlier year, the spatial characteristics of outliers and the question of precursors to outliers. The relationship of outliers to the El Niño/Southern Oscillation, the Pacific Decadal Oscillation and the North Atlantic Oscillation is also considered. A case study examining the relative severities of an outlier drought to a severe drought is also undertaken. Finally, the role of outliers and the greenhouse effect is considered. It is concluded that outliers are a manifestation of stochastic forcing. Copyright © 2006 Royal Meteorological Society.