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Weather Extremes (General) -- Summary
Is earth's weather getting more extreme in response to the warming that has rescued the planet from the chilly grip of the Little Ice Age?  Climate alarmists say that it should be; and in a review of this question, Easterling et al. (2000) go even further, saying that data in support of this proposition "would add to the body of evidence that there is a discernable human affect on the climate."  Of course, the finding of such data would do nothing of the sort; but if they truly believe that it would, they should be equally willing to accept the opposite conclusion, i.e., that lack of such data would call this claim into question, although, of course, it really wouldn't.  It would only refute the climate alarmist claim that warmer weather breeds more extreme weather events.

So what did Easterling et al. discover in their review of the pertinent scientific literature? In their own words, "in some areas of the world increases in extreme events are apparent, while in others there appears to be a decline."  Overall, therefore, they could see no real trend, although they did acknowledge that "the number of intense and landfalling Atlantic hurricanes has declined."  Iskenderian and Rosen (2000) also took up the challenge of the search for change, analyzing two mid-tropospheric temperature data sets of the last half-century for day-to-day variability within each month, season and year. However, they too could find no clear-cut evidence of any significant change in temperature variability for either the Northern Hemisphere or the United States.

But what about the fact that most measures of the economic impacts of weather and climate extremes over the past several decades reveal increasing losses?  In reviewing this question, Kunkel et al. (1999) concluded that "increasing losses are primarily due to increasing vulnerability arising from a variety of societal changes, including a growing population in higher risk coastal areas and large cities, more property subject to damage, and lifestyle and demographic changes subjecting lives and property to greater exposure," particularly since "trends in most related weather and climate extremes do not show comparable increases with time."  Specifically, they found that "increasing property losses due to thunderstorm-related phenomena (winds, hail, tornadoes) are explained entirely by changes in societal factors," and that "when changes in population, inflation, and wealth are considered," there is a downward trend in hurricane losses.  In addition, they report "no apparent trend in climatic drought frequency" and "no evidence of changes in the frequency of intense heat or cold."

Similar conclusions have been reached by van der Vink et al. (1998), who say "we are becoming more vulnerable to natural disasters because of the trends of our society rather than those of nature," as well as Changnon et al. (2000), who say "population growth and demographic shifts are the major factors behind the increasing losses from weather-climate extremes."  The latter authors also conclude "it is reasonable to predict ever-increasing losses even without any detrimental climate changes."

Longer histories of climate provide an even better perspective on the issue.  In a massive tree-ring study conducted in Spain, for example, Manrique and Fernandez-Cancio (2000) developed thousand-year chronologies of both temperature and precipitation, finding that the greatest concentration of extreme climatic excursions was located between 1400 and 1600, with a maximum frequency centered at about 1500.  In fact, they refer to these extreme climatic excursions as "the outstanding oscillations of the Little Ice Age," for which there is no comparable analogue in the entire past millennium.

In view of these several real-world observations, it was interesting to note (see Extreme Weather Events) that on 10 August 1998, the Office of the Vice President of the United States of America issued an official press release, stating that "we are warming the planet and, unless we act, we can expect even more extreme weather - more heat waves, more flooding, more powerful storms, and more drought."  This same message was purveyed to the public about a year later in a series of HOTEARTH advertisements (see "Noticed the Weather Lately?") that specifically mentioned heat waves, droughts, hurricanes and floods.  However, as we noted in responding to the claims of the Vice President, even the IPCC documents of the day were renouncing such outlandish predictions.  Indeed, the organization's 1996 report bluntly states "there is no evidence that extreme weather events, or climate variability, has increased, in a global sense, through the 20th century."  And in our reply to the HOTEARTH ads, we cited several studies that contradict their contentions with respect to each of the weather events they claim to be getting worse.

In conclusion, the climate alarmists are clearly way off base with respect to their predictions of rising air temperatures increasing the frequency and severity of extreme weather events, which is really a very straightforward question.  And if they can't even get this simple concept right, there's little reason to believe they are correct on the much more complex question of man's potential impact on the planet's climate.  Why anyone would continue to believe them is beyond our comprehension.

References
Changnon, S.A., Pielke Jr., R.A., Changnon, D., Sylves, R.T. and Pulwarty, R.  2000.  Human factors explain the increased losses from weather and climate extremes.  Bulletin of the American Meteorological Society 81: 437-442.

Easterling, D.R., Evans, J.L., Groisman, P.Ya., Karl, T.R., Kunkel, K.E., and Ambenje, P.  2000.  Observed variability and trends in extreme climate events: A brief review.  Bulletin of the American Meteorological Society 81: 417-425.

Iskenderian, H. and Rosen, R.D.  2000.  Low-frequency signals in midtropospheric submonthly temperature variance.  Journal of Climate 13: 2323-2333.

Kunkel, K.E., Pielke Jr., R.A. and Changnon, S.A.  1999.  Temporal fluctuations in weather and climate extremes that cause economic and human health impacts: A review.  Bulletin of the American Meteorological Society 80: 1077-1098.

Manrique, E. and Fernandez-Cancio, A.  2000.  Extreme climatic events in dendroclimatic reconstructions from Spain.  Climatic Change 44: 123-138.

van der Vink, G., Allen, R.M., Chapin, J., Crooks, M., Fraley, W., Krantz, J., Lavigne, A.M., LeCuyer, A., MacColl, E.K., Morgan, W.J., Ries, B., Robinson, E., Rodriquez, K., Smith, M. and Sponberg, K.  1998.  Why the United States is becoming more vulnerable to natural disasters.  EOS, Transactions, American Geophysical Union 79: 533, 537.