Bonsal, B. and Regier, M. 2007. Historical comparison of the 2001/2002 drought in the Canadian Prairies. Climate Research 33: 229-242.
What was done
The authors compared the spatial extent and severity of the 2001/2002 Canadian Prairie drought to previous droughts of this region - based on data obtained from 21 reporting stations in southern Alberta, Saskatchewan and Manitoba - during the 1915-2002 period of reasonably extensive instrumental records, using two different drought indicators: the Palmer Drought Severity Index (PDSI) and the Standardized Precipitation Index (SPI) at several temporal scales.
What was learned
Bonsal and Regier report that "over the agricultural region of the Prairies, 2001 and 2002 generally ranked high in terms of spatial extent and severity of drought," and that "at some stations the 2001/2002 drought was the most severe one on record." Nevertheless, they state that "the SPI and PDSI as drought indicators revealed that the worst and most prolonged Prairie-wide droughts during the instrumental record (1915-2002) ... occurred in the early part of the 20th century (1915 through the 1930s)."
What it means
Citing human-induced global warming as the cause (primarily as a result of mankind's CO2 emissions), Al Gore declared in his 21 March 2007 testimony before the U.S. Senate that "droughts are becoming longer and more intense." In the case of droughts on the Canadian Prairies, however, this statement is far from the truth, particularly when it is realized that atmospheric CO2 concentrations ranged from only about 298 to 307 ppm from 1915 through the 1930s, which is about 70 ppm less than the values registered in 2001/2002, yet the droughts of that earlier CO2-depleted period were both "longer and more intense" than the drought of 2001/2002, even though Gore and his supporters claim the latter years were the warmest of the past millennium or more, which makes Gore's claim even more ridiculous, especially in light of the fact that Bonsal and Regier note, and rightly so, that "droughts are projected to dramatically increase in both spatial extent and severity" when temperatures rise.
So, we know when the most severe and widespread droughts of the historical record occurred on the Canadian Prairies (1915 through the 1930s); but as for why they occurred at that time is anybody's guess, although we definitely know they were not caused by anthropogenic CO2 emissions!Reviewed 10 October 2007