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"Noticed the Weather Lately?"
Volume 2, Number 22: 15 November 1999

This innocuous question introduces a one-page "HOTEARTH" advertisement in the 25 October 1999 New Republic.  What is it selling?  The idea that "IT'S TIME TO START FIXING GLOBAL WARMING."

The ad states that "nearly every scientist who is an expert on climate says that global warming is real and having an effect."  Of course it is.  It wasn't much more than a century ago that the planet was shivering through what has come to be known as the "Little Ice Age," and the ongoing recovery from that less-than-desirable climatic excursion is indeed "real and having an effect."  In fact, it is returning the globe to a condition akin to what it was like during the preceding warm period that has come to be known as the "Little Climatic Optimum," so named because everyone who has studied the two climatic regimes has come to the conclusion that the warm interlude was much to be preferred over the protracted cold spell that followed it.

This fact, however, is not the "real effect" that the ad is attempting to sell.  Quite to the contrary, the ad (which was paid for by the National Environmental Trust) claims that the warming of the last century is "making our weather more extreme."  In what ways?  Well, the ad's creators throw out words like heat waves, droughts, hurricanes and floods, which they say are costing us "three times more than a decade ago."

The rhetoric sounds impressive; but is it true?  Is the global warming that has gradually ameliorated the environmental stresses and strains of the Little Ice Age really making our weather more extreme in these several unfriendly ways?  Let's do what any rational person would do if he or she knew how to do it, but what the copywriters of the National Environmental Trust apparently did not do.  Let's check out the peer-reviewed scientific literature and see what the real "experts on climate" have to say.

Let us consider, first of all, the general two-part claim that the weather is getting more extreme and that it is getting that way as a consequence of global warming.  Kunkel et al. (1999) recently analyzed historical trends of several different types of extreme weather events, together with their societal impacts.  They found that most measures of the economic impacts of weather and climate extremes over the past several decades do indeed reveal increasing losses, which is what the HOTEARTH ad proclaims.  However, they also found that "trends in most related weather and climate extremes do not show comparable increases with time," which flies in the face of what the ad suggests.

How is this dichotomy explained?  In the words of the scientists who conducted the study, the increasing economic 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."

Much the same conclusion has been reached by van der Vink et al. (1998), who conclude that "we are becoming more vulnerable to natural disasters because of the trends of our society rather than those of nature."  Specifically, they note that (1) more people are moving into coastal areas that are vulnerable to natural hazards, (2) the effect of this population shift is amplified because the people who are moving into these areas come from the wealthier segment of society, and (3) the wealth of these wealthy people has been rising at a dramatic rate.  Today, for example, millionaires are a dime a dozen; and one almost has to be a milti-billionaire to attract attention.

With respect to some of the specific weather phenomena they studied, Kunkel et al. note that "increasing property losses due to thunderstorm-related phenomena (winds, hail, tornadoes) are explained entirely by changes in societal factors."  They also report there is "no apparent trend in climatic drought frequency" and "no evidence of changes in the frequency of intense heat or cold waves."  With respect to hurricanes, in fact, they find that when changes in population, inflation, and wealth are considered, there is an actual downward trend in damages.

In another study of planetary storminess, Key and Chan (1999) also found no evidence of any global trend.  They did, however, find there were fewer low-pressure cyclones during warmer El Niņo years than during cooler La Niņa years, refuting the oft-made claim that warmer weather leads to more storms.  Should we thus wish for more warmer El Niņo years?  Perhaps we should, for in a study of the plusses and minuses of weather events attributable to the El Niņo episode of 1997-98, relative to human lives and the economy of the United States, Changnon (1999) counted 4.5 billion dollars and 189 lives lost, but 19.5 billion dollars and 850 lives saved!  And in a comprehensive study of United States hurricane damage, Pielke and Landsea (1999) examined all 22 El Niņo years and all 22 La Niņa years that occurred between 1925 and 1997, finding twice the dollar amount of damages in cooler La Niņa years compared to warmer El Niņo years.  In addition, they found average hurricane wind speeds in warmer El Niņo years to be significantly lower than in cooler La Niņa years.

In another extensive survey of hurricanes of the North Atlantic, Gulf of Mexico and Caribbean, Landsea et al. (1999) found decreasing trends over the period 1944-1996 for (1) the total number of hurricanes, (2) the number of intense hurricanes, (3) the annual number of hurricane days, (4) the maximum attained wind speed of all hurricane storms averaged over the course of a year, and (5) the highest wind speed associated with the strongest hurricane recorded in each year.

In view of these several real-world scientific observations, we are prompted to ask ourselves a couple of simple questions.  Has it warmed over the past fifty to one hundred years?  Yes.  Have extreme weather events gotten worse?  No.  Does global warming do what the National Environmental Trust ad says it does?  Not on our planet.  And not even in many of the climate models that have created all the fuss about the subject.

Consider, for example, the findings of Walsh and Pittock (1998), who studied the ability of climate models to predict effects of global warming on tropical cyclones.  They found that (1) "there is little relationship between SST (sea surface temperature) and tropical cyclone numbers in several regions of the globe," (2) "there is little evidence that changes in SST, by themselves, could cause change in tropical cyclone numbers," (3) "regional changes in tropical cyclone numbers caused by possible changes in the characteristics of ENSO (El Niņo-Southern Oscillation) in a warmer world are likewise unknown," (4) "evaporative feedbacks may lower SSTs in the central region of a tropical storm, thus tending to minimize any increase in intensity," (5) "the models suggest that the tropical atmosphere will become more stable," (6) "this may tend to limit intensities," (7) "under enhanced greenhouse conditions, the number of (model-predicted) storms is substantially reduced," and (8) "because of the insufficient resolution of climate models and their generally crude representation of sub-gridscale and convective processes, little confidence can be placed in any definite predictions of such effects."

Ah, but what about floods and droughts?  Lins and Slack (1999) point out that floods and droughts cause more damage annually in the United States than any other natural disaster and that damages due to both of these phenomena have been increasing with time.  As you could probably guess by now, however, the story behind these headlines is pretty much the same as that behind the hurricane hype.  In the words of the two investigators, "most of the flood damage increase stems from continuing urban and suburban development on floodplains" and "drought vulnerability increase is from development in regions of lower renewable water supplies."

Lins and Slack's findings relative to trends in the actual physical phenomena of floods and droughts are even more eye-opening.  Their analysis of more than 1500 streamflow gauges in the United States reveals that "the conterminous U.S. is getting wetter, but less extreme."  It is difficult to conceive of a better consequence of increasing temperatures.  As the climate has warmed over the past century, the United States has gotten wetter in the mean (which is great for thirsty crops, livestock and people) and less variable at the extremes (which is also great for thirsty crops, livestock and people).  Indeed, in a study of the frequency and severity of drought in the central United States over the last two thousand years, Woodhouse and Overpeck (1998) found that the most recent century - wherein a certain degree of global warming has undeniably occurred - has been characterized by droughts of "moderate severity and comparatively short duration, relative to the full range of past drought variability."

Clearly, both the claims and the implications of the HOTEARTH advertisement of the National Environmental Trust are fallacious.  Pielke (1999), for example, lists as one of nine prominent fallacies of floods the claim that "damaging flooding in recent years is unprecedented because of 'global warming'."  And the study of Gan (1998) in Canada confirms that "the evidence is insufficient to conclude that warmer climate will lead to more severe droughts."

So, the next time someone like the National Environmental Trust asks you if you've noticed the weather lately, tell them you have, and that it's getting better, not worse.  And tell them that they have global warming to thank for it.

Dr. Craig D. Idso
Dr. Keith E. Idso
Vice President

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.

Gan, T.Y.  1998.  Hydroclimatic trends and possible climatic warming in the Canadian Prairies.  Water Resources Research 34: 3009-3015.

Key, J.R. and Chan, A.C.K.  1999.  Multidecadal global and regional trends in 1000 mb and 500 mb cyclone frequencies.  Geophysical Research Letters 26: 2053-2056.

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.

Landsea, C.N., Pielke Jr., R.A., Mestas-Nunez, A.M. and Knaff, J.A.  1999.  Atlantic basin hurricanes: Indices of climatic changes.  Climatic Change 42: 89-129.

Lins, H.F. and Slack, J.R.  1999.  Streamflow trends in the United States.  Geophysical Research Letters 26: 227-230.

Pielke Jr., R.A.  1999.  Nine fallacies of floods.  Climatic Change 42: 413-438.

Pielke Jr., R.A., 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.

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.

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.

Woodhouse, C.A. and Overpeck, J.T.  1998.  2000 years of drought variability in the central United States.  Bulletin of the American Meteorological Society 79: 2693-2714.