Interaction of climatic variability with climatic change

Abstract

Climatic simulations suggest that only slight changes in climatic variability are likely to be induced owing to greenhouse warming, and that these changes will project onto existing modes of climatic variability. A lesser studied aspect of the interaction of climatic variability with climatic change is how such a mutual interaction manifests itself as interannual climatic fluctuations. A number of examples are examined in this paper using simulations made with the Commonwealth Scientific and Industrial Research Organization (CSIRO) Mark 2 coupled climatic model. The simulations included an ensemble based on four Special Report on Emission Scenarios (SRES) cases, as well as individual ensembles for two selected SRES cases. In general, the intra‐ensemble variability for a given SRES case was quite similar to the inter‐ensemble variability of the four individual SRES cases. Time series of selected climatic variability and probability density function displays are used to illustrate the character of climatic variability for simulations out to 2100. Other examples include variations in droughts and pluvial events, and associated runoff, as the greenhouse effect progresses. The differing responses in the frequency of dry events among four SRES cases are also illustrated. The outbreak of cold events around 2050 is used to highlight the impact of climatic variability. Finally, case studies involving two large‐scale climatic phenomena are used to show the ongoing dominance of climatic variability.