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Blizzards -- Summary
In what serves as a good introduction to the subject of snowstorms or blizzards, and how global warming might possibly impact them, Changnon and Changnon (2006) have written that "global climate models predict that more weather extremes will be a part of a changed climate due to greenhouse gases," that such a change of climate "is anticipated to result in alterations of cyclone activity over the Northern Hemisphere (Lawson, 2003)," and that "a change in the frequency, location, and/or intensity of extratropical cyclones in the mid-latitudes would alter the incidence of snowstorms [our italics]," citing as further authority for this view the paper of Trenberth and Owen (1999). Hence, it was only natural that the two U.S. researchers would employ real-world data from the United States to evaluate the robustness of this prediction.

As the Changnons describe it, "a climatological analysis of the spatial and temporal distributions of ... damaging snowstorms and their economic losses was pursued using property-casualty insurance data that consist of highly damaging storm events, classed as catastrophes by the insurance industry, during the 1949-2000 period," and in support of this approach to the subject, they write that the United States National Academy of Sciences has identified insurance catastrophe data as "the nation's best available loss data (National Research Council, 1999)."

So what did they find?

The father-and-son research team reports that "the incidence of storms peaked in the 1976-1985 period," but that snowstorm incidence "exhibited no up or down trend during 1949-2000," although national monetary losses did have a significant upward time trend that was indicative of "a growing societal vulnerability to snowstorms." Hence, they concluded that "the temporal frequency of damaging snowstorms during 1949-2000 in the United States does not display any increase over time, indicating that either no climate change effect on cyclonic activity has begun, or if it has begun, altered conditions have not influenced the incidence of snowstorms."

Also working in the conterminous United States, Schwartz and Schmidlin (2002) examined past issues of Storm Data -- a publication of the U.S. National Weather Service (NWS) -- to compile a blizzard database for the years 1959-2000, which they analyzed to determine blizzard temporal trends, spatial patterns and relationships with ENSO. This work identified a total of 438 blizzards in the 41-year record, yielding an average of 10.7 blizzards per year. Year-to-year variability, however, was quite significant, with the number of annual blizzards ranging from a low of 1 in the winter of 1980/81 to a high of 27 during the winter of 1996/97.

Linear regression analysis revealed a statistically significant increase in the annual number of blizzards during the 41-year period; but the total area affected by blizzards each winter remained relatively constant and showed no trend. If these observations are both correct, then average blizzard size was much smaller at the end of the 20th-century's "unprecedented warming" than it was four decades earlier. As the researchers note, however, "it may also be that the NWS is recording smaller, weaker blizzards in recent years that went unrecorded earlier in the period, as occurred also in the official record of tornadoes in the United States." Last of all, with respect to ENSO effects, a weak but marginally significant relationship was noted, with a tendency for two to three more blizzards to occur during La Niņa winters than during El Niņo winters.

The frequency and intensity of extreme weather events are typically projected to increase in response to global warming; and the data of this study of U.S. blizzards suggest that frequency may possibly have responded as predicted, but if it did, intensity likely did the opposite. On the other hand, Schwartz and Schmidlin suggest that the reported increase in blizzard frequency may well be due to an observational bias that developed over the years, for which there is a known analogue in historical observations of tornados. In addition, we note there were fewer blizzards in warmer El Niņo winters than in cooler La Niņa winters, which also runs counter to predictions of more extreme weather in warmer as opposed to cooler periods of time.

Across the border up in Canada, Khandekar (2003) conducted a study of extreme weather events for the government of Alberta; and he writes that his research led him to conclude that "extreme weather events such as heat waves, rain storms, tornadoes, winter blizzards [our italics], etc., are not increasing anywhere in Canada at this time." And in discussing these findings he additionally notes that a recent special issue of Natural Hazards (Vol. 29, No. 2, June 2003) concludes much the same thing about other parts of the world, specifically citing a survey article by Robert Balling that concludes "there is no significant increase in overall severe storm activity (hurricanes, thunderstorms/tornadoes, winter blizzards [our italics]) across the conterminous United States," as well as an article by Stanley Changnon, which concludes that "increasing economic loss due to weather extremes in the conterminous United States is a result of societal change and not global warming."

Also working in Canada, Lawson (2003) extracted blizzard data for a number of locations within the Prairie Ecozone of the western part of the country from meteorological records for the period 1953-1997 and analyzed them for trends in snowstorm occurrence and severity. This effort detected no significant trends in central and eastern locations. However, there was a significant downward trend in blizzard frequency in the more westerly part of the prairies; and Lawson notes that "this trend is consistent with results found by others that indicate a decrease in cyclone frequency over western Canada." He also notes that the blizzards that do occur "exhibit no trend in the severity of their individual weather elements," and in discussing his findings, he says that the trends found "serve to illustrate that the changes in extreme weather events anticipated under climate change may not always be for the worse."

Last of all, Gulev et al. (2001) developed and analyzed a winter (January-March) climatology of 1000-mb or lower sea-level-pressure storms for the entire Northern Hemisphere based on NCEP/NCAR reanalysis data for the period 1958-1999. In doing so, they discovered that the mean number of such cyclones over the Northern Hemispheric winter was 234, although there was pronounced interannual and spatial variability in the record. Nevertheless, linear trend estimates revealed a statistically significant annual decline of 1.2 cyclones per year, suggesting that at the end of the 20th century the Northern Hemisphere experienced 50 fewer cyclones than it had experienced 42 years earlier. Other analyses also suggested that Northern Hemispheric winter cyclones had intensified at quicker rates and reached greater maximum depths (lower sea level pressure) at the end of the record than they had at its beginning. However, the wintertime cyclones also experienced shorter life cycles, as they dissipated more quickly at the end of the record than at the beginning.

Based on these observations, it would appear that winter storms in North America at the end of the 20th century matured faster, but dissipated quicker, than they had done four decades earlier. Could this change have been the result of global warming? According to the three researchers, the phenomenon is more likely connected to large-scale features of atmospheric variability, such as the North Atlantic Oscillation and the North Pacific Oscillation. As for the large decrease in the annual number of Northern Hemispheric cyclones over the 42-year period, we note that this observation runs contrary to climate-alarmist predictions, which suggest that the frequency of such events should increase as a result of global warming. Once again, therefore, the predictions of the climate models appear to be diametrically opposed to the testimony of nature.

References
Changnon, S.A. and Changnon, D. 2006. A spatial and temporal analysis of damaging snowstorms in the United States. Natural Hazards 37: 373-389.

Gulev, S.K., Zolina, O. and Grigoriev, S. 2001. Extratropical cyclone variability in the Northern Hemisphere winter from the NCEP/NCAR reanalysis data. Climate Dynamics 17: 795-809.

Khandekar, L. 2003. Comment on WMO statement on extreme weather events. EOS, Transactions, American Geophysical Union 84: 428.

Lawson, B.D. 2003. Trends in blizzards at selected locations in the Canadian prairies. Natural Hazards 29: 123-138.

National Research Council. 1999. The Costs of Natural Disasters: A Framework for Assessment. National Academy Press, Washington, DC, USA.

Schwartz, R.M. and Schmidlin, T.W. 2002. Climatology of blizzards in the conterminous United States, 1959-2000. Journal of Climate 15: 1765-1772.

Trenberth, K.E. and Owen, T. 1999. Workshop on indices and indicators for climate extremes: Breakout group A: Storms. Climatic Change 42: 9-21.

Last updated 12 March 2008