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Abrupt Climate Change
Volume 10, Number 29: 18 July 2007

Climate alarmists are always talking about abrupt climate changes resulting from earth's rising temperature passing some ominous "tipping point" that triggers the occurrence of more numerous and severe storms, floods and droughts. One need only look to Al Gore's testimony of 21 March 2007 before the United States Senate's Environment and Public Works Committee for confirmation of this fact, wherein he states - without equivocation - that "droughts are becoming longer and more intense," but, of course, without offering any evidence in support of his contention.

To fill this gaping void with respect to drought, we here report the findings of Narisma et al. (2007), who analyzed "global historical rainfall observations to detect regions that have undergone large, sudden decreases in rainfall [that] are statistically significant at the 99% level, are persistent for at least ten years, and .. have magnitudes that are [mostly] 10% lower than the climatological normal (1901-2000 rainfall average)."

Working with the gridded high-resolution (0.5 x 0.5 degrees of latitude and longitude) global precipitation data set of Mitchell et al. (2004), which covers the period 1901-2000, the four researchers identified 30 drought episodes throughout the world that satisfied these stringent criteria during the 20th century. Among this major drought directory was the sudden and prolonged Sahel drought of Africa in the late 1960s, the United States Dust Bowl of the 1930s and Southwest drought of the 1950s (which also affected parts of Mexico), the strong and persistent droughts that occurred in northeast China in the 1920s, in Kazakhstan and regions of the former Soviet Union in the late 1930s, in southeast Australia in the late 1930s, and in southern Africa and eastern Europe in the 1980s, as well as the World War II droughts of 1937-1945 and the droughts that occurred over large regions of East India and Bangladesh in the 1950s.

With respect to the temporal distribution of the 30 severe and persistent droughts identified by Narisma et al., seven of them occurred during the first two decades of the 20th century (1901-1920), seven occurred during the next two decades (1921-1940), eight during the middle two decades of the century (1941-1960), but only five during the next two decades (1961-1980), and a mere three during the final two decades of the century (1981-2000), which is not at all what one would have expected if the climate-alarmist thesis that is propounded by Gore and his followers was correct.

So just what is the situation here? The scientists who performed the analysis note that the 30 major droughts they identified were "mostly located in semi-arid and arid regions" that "are naturally prone [our italics] to large fluctuations." And it's as simple as that. The 30 major droughts of the 20th century were likely natural in all respects; and, hence, they are "indicative of what could also happen in the future," as Narisma et al. state in their concluding paragraph. And happen they will. Consequently, the next time a serious drought takes hold of some part of the world and the likes of Al Gore blame it on the "carbon footprints" of you and your family, ask them why just the opposite of what their hypothesis suggests actually occurred over the course of the 20th century, i.e., why, when the earth warmed - and at a rate and to a degree that they claim was unprecedented over thousands of years - the rate-of-occurrence of severe regional droughts actually declined.

Sherwood, Keith and Craig Idso

References
Mitchell, T.D., Carter, T.R., Jones, P.D., Hulme, M. and New, M. 2004. A comprehensive set of high-resolution grids of monthly climate for Europe and the globe: The observed record (1901-2000) and 16 scenarios (2001-2100). Tyndall Center Working Paper 55, Norwich, UK.

Narisma, G.T., Foley, J.A., Licker, R. and Ramankutty, N. 2007. Abrupt changes in rainfall during the twentieth century. Geophysical Research Letters 34: 10.1029/2006GL028628.