And extremely bad logic! (Extreme Weather).

This summer's floods in Europe were an unmitigated tragedy, as is the ongoing severe drought plaguing the eastern United States. In 1998, Hurricane Mitch killed roughly 10,000 in Central America. Annually, floods in China force thousands from their homes. And the list goes on.

These disasters all have something in common. In every case, a senior and responsible government official blamed them on global warming; in each case, they were wrong. But in no case have I heard the United Nations counter such misstatements. It is time for this to change, for exaggerations of the threat of climate change only serve to cheapen the environmental ethic.

Alas, much of the current rhetoric can be justified by United Nations documents. In 1995, in its Second Assessment Report on climate change, the Intergovernmental Panel on Climate Change (IPCC), of which I am a member, wrote: "Warmer temperatures will lead to a more vigorous hydrological cycle; this translates into prospects for more severe droughts and/or floods in some places and less severe droughts and/or floods in other places."

This unfortunate statement allows any official to blame any drought, storm or flood on global warming. Critics of global warming extremism, including myself, waxed apoplectic, because this 1995 IPCC statement even allows weather that is more normal than average to be caused by global warming. It was a truly universal and therefore scientifically meaningless statement. This criticism apparently worked, for no similar text appears in the IPCC 2001 Third Assessment Report.

Nevertheless, the statement has had its effect upon a citizenry who is, in general, poorly educated about environmental matters. So it's time to set the record straight:

Tropical cyclones. Several scientists, notably Christopher Landsea of the United States National Oceanic and Atmospheric Administration's Hurricane Research Division, have demonstrated that there is simply no global trend in the frequency of tropical cyclones (hurricanes, typhoons, and tropical storms). Even more interesting is an apparent drop in the annual average wind maximum measured in storms in the Atlantic Basin (see Figure 1). This was published by the IPCC, but a Nexis-Lexis search of news stories reveals that not one United Nations official has ever noted its existence.

Also, the computer models that scientists often rely on for projecting the future climate under an enhanced greenhouse effect simply exhibit no consensus on tropical cyclones. While some models predict more tropical cyclones, others predict less. But one thing everyone can agree on is that they impact increasingly crowded beaches. In the United States, the value of property along the Atlantic Coast is approximately $10 trillion, or slightly more than the average economic production of the nation as a whole. One big storm on the right track will now cost $100 billion and may put some large insurance concerns into bankruptcy. It is foolish, but when this happens the blame will be on global warming and unless there is a change of heart, no one of consequence will object.

Drought. Worldwide precipitation appears to be increasing slightly as the planet warms. This is especially true in the mid-latitude breadbaskets, where the change has been about 10 per cent over the last 100 years. The common argument is that even though precipitation increases, temperatures rise so rapidly that the increased rain evaporates along with any remaining surface moisture. This contention can be easily examined in light of the current American drought, which the Governor of Maryland, Parris Glendening, blamed on global warming.

While rainfall in the United States has increased by about 10 per cent in the last century, or approximately 75 millimetres, nationwide temperatures have risen about 0.5[degrees]C. C. That temperature change results in an average evaporation increase of about 15mm. As a result, it is obvious that the United States is getting wetter, not drier.

This can be verified by examining hydrological indices, such as the popular Palmer Drought Severity Index, which measures both extreme dryness and wetness (see Figure 2). It is apparent that there is no change in the drought in the country, and there is actually a statistically significant increase in wetness.

Similar considerations apply to the Indian monsoon. A recent article in the prestigious Journal Science (Anderson et al., 2002) received much press, particularly before the recent World Summit on Sustainable Development in Johannesburg, because it found subtle changes in the monsoon that correlate with global temperatures.

What seems to have been lost in the hype was this portion of the text: "The trend in all-India rainfall, although positive, is small and statistically insignificant; however, the regional and year-to-year variability is large. Using historical data [other researchers] found no change in the last 200 years in the frequency of extreme drought events."

Floods. A tremendous amount of exaggeration has developed around scientific studies showing increases in the frequency of what United States Vice-President Al Gore called "torrential" rains. The original work is largely from Thomas Karl, who heads the United States National Climatic Data Center. He found that there was an increase in the frequency of rainfall of more than 50mm per day over the country. This is hardly "torrential", as most of the increase was from storms between 50mm and 75mm. Analysis of his data reveals that the increase in flooding rains--storms producing more than 125mm per day--works out to two instances per lifetime, or 2 in 27,500 days. This reality is nowhere to be found in the reports of the IPCC on climate change.

Changes in European rainfall appear to be of the same magnitude. As a result, it is scientifically indefensible to relate the recent flood disaster to global warming. The change in frequency is so small as to be undetectable in any socially significant sense.

In this age of hundreds of channels of television and universal internet access, those who misrepresent climate change by exaggeration to the detriment of the environment and the environmental movement are soon corrected. It is time to stop the exaggeration, and I look for the United Nations to take the lead.

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Patrick J. Michaels, Senior Fellow in Environmental Studies at the Cato Institute (Washington, D. C., United States), is Research Professor of Environmental Sciences at the University of Virginia and is Virginia State climatologist. He has been President of the American Association of State Climatologists and Program Chair of the Applied Climatology Committee of the American Meteorological Society Mr. Michaels, who is a member of IPCC, has published over 200 scientific articles on climate and its impact on society including "The Satanic Gases: Clearing the Air About Global Warming", published in 2000 by Cato Books.