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i The Science & Environmental Policy Project, 2101 Wilson Blvd., #1003, Adington, VA 22201 .(703) 527-0130 Scientific myths ride in on hurricane winds Mlcheele Br PATRICKJ, MICHAELe ow that Hurricane Andrew - the most expensive vortex in recorded history - has come and gone, blowing everything to bits in its path, the usual political suspects have substituted one strong wind for another. In fact, the only thing that one could forecast with more confidence than Andrew's path ("a well-be- haved hurricane;' whatever that means, from the forecasters point of view) is the likelihood PatrickJ. that it would be used to enhance Afichaefs, a pro- the vision oflurid environmental fessorofenvi-, change because of man's pemi- ronmentalsci- cious influence on the atmo- enres at the Uni- sphere. vers'rryaJVir- At least that's what readers of ginia, is Newsweek saw: "Many scientists affiliated witk are also confident enough to say: TheScience& look at Andrew; that may be Environmental what a greenhouse world would Pnlicy Projectin be like." Washington. Pretty subjective stu/E In fact, Hismostrecent the scientific core of all this is boakis Sound MIT scientist Kerry Emanuel's and Fury: The 1987 Nature paper that calcu- Science and lates that an increase in the 1'oliticsof strength of hurricanes could Global Warm- accompany global warming, This ing, paper, which is an interesting theoretical calculation, includes assumptions about the behavior of hurricanes that are known to be untrue, and which are freely acknowiedged by the author. . 8 40b17 LVLOZ VIEWPOINT One of these is that hurricanes, sured a lowest Pressure ol' 26.23 which require sea surface tem- inches in Hurricane Gilbert in the peratures in excess of 27 degrees Cel- Western Caribbean. This beat the sius,donolreducethetempemtureqf previous Atlantic record, by a grand [he ocean over which they travel, total of 0.15 inches, that was mea- Everyone knows that they do, and sured when the great Labor Day hor- Emanuel only assumed it as a matter ricane of 1935 augured into thc Flor- of convenience in his calculations. ida Keys, Togiveanideaofhowmucheool- , tnfact,il'sonlyinlhelast35years ing hurricanes cause in the real world, orso-sincethe 1935s1orm-that consider Gilbert in 1988. After it hit "'e ve been dropping barometers via the Yucatan peninsula, Gilbert aimraR into the eyes of hurticanes. unspun into a garden-variety system (No, thank you. You can't pay me burblingacrosstheBayofCampeches enough to do it.) One thing we've That eaused ?real consternation in found a bht ti.e,gthev lowest pres- tithe news media, which likes desWC• sure rises) before they hit land. Gil- ve hurricanes about as much as ~rt s pressure rose considembly - Democmts love big unemployment to values above those noted in Flor- fgures- But because it had Qenemted ida during the 1935 storm -before it so much interest earlier, while setting hit Commel. If we assume that the the record for the lowest barometer 1935 storm also filled up a bit before even recorded over the Atlantic itdrownedatminfulofescapeesfrom Oeenn, Gilbert became the most the Keys, it seems obvious that its instrumented cyclone in human his• loweslpressurewasprobablybeneath tOry' that of Gilbert's. As Gilbed chugged between the (2) The most severe hurricanes are Yucatan and La Pesca ("the fish"), related to global mannirtg. Unmiti- Mexico, where final landfall waa gated balderdash. Only Iwo "Cate- made, even as a moderate hurrmcaee it cooled the ocean 5 degrees Celsiuk from 31 C to 26 C, which is beneath the value necessary to create subsa quent hurricanes. This is equivalent to the difference between summer and winter temperatures of those waters, and serves more to demon- strate that the hurricane is as much a natural brake on surface warming as it is a product of warm temperatures. Having said all that, recent events provide an appropriate forum lobeal on a few hurricane myths, pmticu- Iarly as they might be affected by a pulativeglobal warming: (1) lfurricanes are bernming more ,severe. This nonsense sprang up in September 1988, when aircraft mca- gory 5" hurricanes, government dia- lect for "big time," have hit this country. The aforementioned 1935 storm hit when temperatures were very warm. The other 5-blast was Camille in 1969, which tore up (he Mississippi Gulf Coast with profound dispatch. It occurred when the hemi- sphere was near ilsc+pldest lempem- lure for the last half century. Here's a chronology of all of the 20th Century "Category 4" storms to hit the United States with respect to global warming: Andrew occurred as hemispheric temperatures approached their lowest valucs mea- sured in the 14-year satellite record, and a0er a rapid cooling from Mt, Pinalubo. Hugo(1989) occurred in a SUNDAY. SEPiEMBER20, 1992 Ww1ami Herald Wissill If history is to be our guide, a modest warming will produce more wimpy hurricanes but about as naany Gilberts orAndrews or Camilles or Labor Day sockos as we have already seen. very warm year, Carla (1961)- the storm that made Dan Rather famous - Donna (1960), Audrey (1957) and Hazel (1954) all occurred during a cool period. Prior to 1950 hurricanes weren't named, but il W„s still cool for the 1947 Category 4, Similar sdorms in 1928 and 1926 occurred during rela- tively warm times, and the 1919, 1915, 1909 and 1900 storms all occurred during colder than normal temperatures - the last, the natural disaster with the highest number of fatalities in the history of the United States. Score for Category 4s: Three during warm years, and 10 when tem- peratures were below average. (,f) HWrieallP Sel'Prily will increase in a wanned aror)d. This one, based upon a casual read of Emanuel's paper, flies in the face of what has been obsened in the 20th Century. While there hasn't been much overa8 temperature change,there have been some warm times (like the 1930s and Ihe 1980s) and some cold times (1940-1975). Writing in the scienlilic journal Meteorology apd Almo- spheric Physics in 1990, scientisl Sherwood ldso and his colleagues found that indeed there are more /rapical cyclones (the generic term for tropical slorms and hurricanes) in warm years, but that they tend to be ,reaker. (4) Afmaut all trnpical civ'les are bad netcs. Hardly. While it is Irue for the relatively uncommon Category 4 and 5 hurricanes, a landmark 1967 study by George Cry, of ine U.S. Department of Commerce, dcmon• stmled that as much as 50 percent of the late summer rainfall that nor- mally occurs in the Southcast and Atlantic Coast rcgions of the United States results from thc much weaker Category I and 2 hurricanes and trop- iical storms. Regional agriculture is heavily dependent upon this precipi- tation. Much of the double-cropped soybean culture of the Southeast is in its period of maximum moisture requiremcnt just ss,hen these storms are expected I, Where does that leave us in a warmed world? First, as I have said repeatedly in the last few years, observed data suggest wc won't see Ihe apocalyptic warming that is in vogue, but we should see some. If his- tory is 10 be our guide, a modest warming will produce more wim(fy hurricanes but about as many Gd• 'bcrts or Andrews or Camilles or Labor Day sockos as we have already seen. Coastal agriculture will 0ourish, but every few years someplace is going to get pulverized. Every suc- ceeding blast is likely to cost more money because of increased coastal Populalion and monetary inflation. And as Ihc damage figures go up, up and auay, folks will likely blame global warming, instead of their owrt desire to live in hnrm's way. 11 I