The anti-CO2 crowd typically makes three different claims about the likely influence of potential 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. In this summary, we test the validity of the last of these three assertions.
Changnon (1999) determined that adverse weather events attributed to the El Niņo of 1997-98 negatively impacted the United States economy to the tune of 4.5 billion dollars and contributed to the loss of 189 lives, which is serious indeed. On the other hand, he determined that El Niņo-related benefits amounted to approximately 19.5 billion dollars - resulting primarily from reduced energy costs, industry sales, and the lack of normal hurricane damage - and that a total of 850 lives were saved due to the reduced amount of bad winter weather. Thus, the net impact of the 1997-98 El Niņo on the United States, according to Changnon, was "surprisingly positive," in stark contrast to what was often reported in the media and by climate alarmists, who tend, in his words, "to focus only on the negative outcomes."
Another of the "surprisingly positive" consequences of El Niņos is their tendency to moderate Atlantic hurricane frequencies. Working with data from 1950 to 1998, Wilson (1999) determined that the probability of having three or more intense hurricanes during a warmer El Niņo year was approximately 14%, while during a cooler non-El Niņo year the probability jumped to 53%. Similarly, in a study of tropical storm and hurricane strikes along the southeast coast of the United States over the entire last century, Muller and Stone (2001) determined that "more tropical storm and hurricane events can be anticipated during La Niņa seasons [3.3 per season] and fewer during El Niņo seasons [1.7 per season]." And in yet another study of Atlantic basin hurricanes, this one over the period 1925 to 1997, Pielke and Landsea (1999) reported that average hurricane wind speeds during warmer El Niņo years were about six meters per second lower than during cooler La Niņa years. In addition, they reported that hurricane damage during cooler La Niņa years was twice as great as during warmer El Niņo years. These year-to-year variations thus indicate that, if anything, hurricane frequency and intensity - as well as damage - tend to decrease under warmer El Niņo conditions, which is just the opposite of the impression that is typically conveyed to the public by climate alarmists.
Much the same story is filtering out of other parts of the world. In the North Indian Ocean, Singh et al. (2000) studied tropical cyclone data pertaining to the period 1877-1998, finding that tropical cyclone frequency there declined during the months of most severe cyclone formation - November and May - when ENSO was in a warm phase. In New Zealand, De Lange and Gibb (2000) studied storm surge events recorded by several tide gauges in Tauranga Harbor over the period 1960-1998, finding a considerable decline in both the annual number of such events and their magnitude in the latter (warmer) half of the nearly four-decade-long record, additionally noting that La Niņa seasons typically experienced more storm surge days than El Niņo seasons. And in Australia, Kuhnel and Coates (2000) found that over the period 1876-1991, yearly fatality event-days due to floods, bushfires and heatwaves were actually greater in cooler La Niņa years than in warmer El Niņo years.
Apparently, even tiny-brained birds seem to know better than climate alarmists when it comes to the dangers of La Niņa vs. El Niņo. In a study of breeding populations of Cory's Shearwaters on the Tremiti Islands of Italy, for example, Brichetti et al. (2000) found that, contrary to even their hypothesis, survival rates during El Niņo years were greater than during La Niņa years, which they ultimately attributed to the soothing influence of La Niņa on Atlantic hurricanes.
References
Brichetti, P., Foschi, U.F. and Boano, G. 2000. Does El Niņo affect survival rate of Mediterranean populations of Cory's Shearwater? Waterbirds 23: 147-154.
Changnon, S.A. 1999. Impacts of 1997-98 El Niņo-generated weather in the United States. Bulletin of the American Meteorological Society 80: 1819-1827.
De Lange, W.P. and Gibb, J.G. 2000. Seasonal, interannual, and decadal variability of storm surges at Tauranga, New Zealand. New Zealand Journal of Marine and Freshwater Research 34: 419-434.
Kuhnel, I. and Coates, L. 2000. El Niņo-Southern Oscillation: Related probabilities of fatalities from natural perils in Australia. Natural Hazards 22: 117-138.
Muller, R.A. and Stone, G.W. 2001. A climatology of tropical storm and hurricane strikes to enhance vulnerability prediction for the southeast U.S. coast. Journal of Coastal Research 17: 949-956.
Pielke, R.A., Jr. and Landsea, C.N. 1999. La Niņa, El Niņo, and Atlantic hurricane damages in the United States. Bulletin of the American Meteorological Society 80: 2027-2033.
Singh, O.P., Ali Khan, T.M. and Rahman, M.S. 2000. Changes in the frequency of tropical cyclones over the North Indian Ocean. Meteorology and Atmospheric Physics 75: 11-20.
Wilson, R.M. 1999. Statistical aspects of major (intense) hurricanes in the Atlantic basin during the past 49 hurricane seasons (1950-1998): Implications for the current season. Geophysical Research Letters 26: 2957-2960.