Computer model simulations have given rise to three climate-alarmist claims regarding the influence of global warming on ENSO events: (1) global warming will increase the frequency of ENSO events, (2) global warming will increase the intensity of ENSO events, and (3) weather-related disasters will be exacerbated under El Niņo conditions. We have tested the validity of these assertions elsewhere on our web site [see ENSO (Relationship to Extreme Weather)and ENSO (Relationship to Global Warming)], demonstrating they are in conflict with the observational record. In this summary, we highlight additional findings that suggest the virtual world of ENSO, as simulated by state-of-the-art climate models, is also at variance with reality.
A major part of this distortion is due to the inability of climate models to correctly simulate tropical sea surface temperatures. In a comparison of 24 coupled ocean-atmosphere climate models, for example, Latif et al. (2001) report that "almost all models (even those employing flux corrections) still have problems in simulating the SST climatology." They also note that "only a few of the coupled models simulate the El Niņo/Southern Oscillation (ENSO) in terms of gross equatorial SST anomalies realistically." And they state that "no model has been found that simulates realistically all aspects of the interannual SST variability." Hence, because "changes in sea surface temperature are both the cause and consequence of wind fluctuations," and because these phenomena figure prominently in the El Niņo-La Niņa oscillation, it is not surprising that Fedorov and Philander (2000) conclude that current climate models do not do a good job of determining the potential effects of global warming on ENSO.
Plain old human ignorance likely also plays a role in the models' failure to simulate ENSO. According to Overpeck and Webb (2000), there is evidence that "ENSO may change in ways that we do not yet understand," which "ways" have clearly not yet been modeled. White et al. (2001), for example, found that "global warming and cooling during earth's internal mode of interannual climate variability [the ENSO cycle] arise from fluctuations in the global hydrological balance, not the global radiation balance," and that these fluctuations are the result of no known forcing of either anthropogenic or extraterrestrial origin, although Cerveny and Shaffer (2001) make a case for a lunar forcing of ENSO activity, which also is not included in any climate model.
Another example of the inability of today's most sophisticated climate models to properly describe El Niņo events is provided by Landsea and Knaff (2000), who employed a simple statistical tool to evaluate the skill of twelve state-of-the-art climate models in real-time predictions of the development of the 1997-98 El Niņo. They found that the models exhibited essentially no skill in forecasting this very strong event at lead times ranging from 0 to 8 months. They also determined that no models were able to anticipate even one-half of the actual amplitude of the El Niņo's peak at a medium range lead-time of 6 to 11 months. Hence, they state that "since no models were able to provide useful predictions at the medium and long ranges, there were no models that provided both useful and skillful forecasts for the entirety of the 1997-98 El Niņo" [authors' italics].
Given the inadequacies listed above, it is little wonder several scientists have criticized model simulations of current ENSO behavior, including Walsh and Pittock (1998), who say "there is insufficient confidence in the predictions of current models regarding any changes in ENSO," and Fedorov and Philander (2000), who say that "at this time, it is impossible to decide which, if any, are correct." As a result, there is also little reason to believe that current climate models can correctly predict ENSO behavior under future conditions of changed climate.
References
Cerveny, R.S. and Shaffer, J.A. 2001. The moon and El Niņo. Geophysical Research Letters 28: 25-28.
Fedorov, A.V. and Philander, S.G. 2000. Is El Niņo changing? Science 288: 1997-2002.
Kerr, R.A. 1998. Models win big in forecasting El Niņo. Science 280: 522-523.
Landsea, C.W. and Knaff, J.A. 2000. How much skill was there in forecasting the very strong 1997-98 El Niņo? Bulletin of the American Meteorological Society 81: 2107-2119.
Latif, M., Sperber, K., Arblaster, J., Braconnot, P., Chen, D., Colman, A., Cubasch, U., Cooper, C., Delecluse, P., DeWitt, D., Fairhead, L., Flato, G., Hogan, T., Ji, M., Kimoto, M., Kitoh, A., Knutson, T., Le Treut, H., Li, T., Manabe, S., Marti, O., Mechoso, C., Meehl, G., Power, S., Roeckner, E., Sirven, J., Terray, L., Vintzileos, A., Voss, R., Wang, B., Washington, W., Yoshikawa, I., Yu, J. and Zebiak, S. 2001. ENSIP: the El Niņo simulation intercomparison project. Climate Dynamics 18: 255-276.
Overpeck, J. and Webb, R. 2000. Nonglacial rapid climate events: Past and future. Proceedings of the National Academy of Sciences USA 97: 1335-1338.
Walsh, K. and Pittock, A.B. 1998. Potential changes in tropical storms, hurricanes, and extreme rainfall events as a result of climate change. Climatic Change 39: 199-213.
White, W.B., Cayan, D.R., Dettinger, M.D. and Auad, G. 2001. Sources of global warming in upper ocean temperature during El Niņo. Journal of Geophysical Research 106: 4349-4367.