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North American Summer Soil Moisture Availability
Van der Schrier, G., Briffa, K.R., Osborn, T.J. and Cook, E.R. 2006. Summer moisture availability across North America. Journal of Geophysical Research 111: 10.1029/2005JD006745.

One of the many dangers of global warming, according to climate alarmists, is the propensity for rising temperatures to produce longer, more frequent, more severe, and more expansive droughts. But is this oft-repeated claim correct? In the study reviewed here, this question is addressed with respect to the conterminous United States and part of Mexico.

What was done
Using the self-calibrating Palmer (1965) drought severity index (SCPDSI), as described by Wells et al. (2004), the authors constructed maps of summer moisture availability across a large portion of North America (20-50N, 130-60W) for the period 1901-2002 with a spatial resolution of 0.5 latitude x 0.5 longitude.

What was learned
Van der Schrier et al. report that over the area as a whole, "the 1930s and 1950s stand out as times of persistent and exceptionally dry conditions, whereas the 1970s and the 1990s were generally wet." However, they say that "no statistically significant trend was found in the mean summer SCPDSI over the 1901-2002 period, nor in the area percentage with moderate or severe moisture excess or deficit." In fact, they could not find a single coherent area within the SCPDSI maps that "showed a statistically significant trend over the 1901-2002 period."

What it means
Once again, one of the major calamitous predictions of the world's climate alarmists is found to be totally unsupported over a vast area of North America, just as it has also been found to be generally unsupported over most of the rest of the world (see Drought in our Subject Index).

Palmer, W.C. 1965. Meteorological Drought. Office of Climatology Research Paper 45. U.S. Weather Bureau, Washington, DC, USA.

Wells, N., Goddard, S. and Hayes, M.J. 2004. A self-calibrating Palmer drought severity index. Journal of Climate 17: 2335-2351.

Reviewed 13 September 2006