Brown (2000) employed data from Canada and the United States to reconstruct monthly snow cover properties over mid-latitude (40-60°N) regions of North America back to the early 1900s, finding evidence of what he described as "a general twentieth century increase in North American snow cover extent, with significant increases in winter (December-February) snow water equivalent averaging 3.9% per decade." Although this finding is consistent with climate model simulations that indicate increased precipitation in response to global warming, it covers too little time to tell us much about the cause of modern warming.

Moore et al. (2002) studied a longer period of time in their analysis of a 103-meter ice core retrieved from a high elevation site on Mount Logan -- Canada's highest mountain -- which is located in the heavily-glaciated Saint Elias region of the Yukon. From this deep core, as well as from some shallow coring and snow-pit sampling, they derived a snow accumulation record that extended over three centuries (from 1693 to 2000), which indicated that heavier snow accumulation at their study site was generally associated with warmer tropospheric temperatures over northwestern North America.

So what does their record reveal? Over its first half, there is no significant trend in the snow accumulation data. From 1850 onward, however, there is a positive trend that is significant at the 95% confidence level, which indicates that recovery from the cold conditions of the Little Ice Age began in the mid-1800s, well before there was a large enough increase in the air's CO2 concentration for that greenhouse gas to have been responsible for the first part of the century-and-a-half-long warming. This finding is further strengthened by the temperature reconstruction of Esper et al. (2002), which places the start of modern warming at about the same time as that suggested by Moore et al.'s snow data, contradicting the temperature record of Mann et al. (1998, 1999), which puts the beginning of the modern warming trend at about 1910.

The results of other snow studies raise even more unsettling questions about climate-alarmist contentions. Cowles et al. (2002), for example, analyzed snow water equivalent (SWE) data obtained from four different measuring systems -- snow courses, snow telemetry, aerial markers and airborne gamma radiation -- at more than 2000 sites in the eleven westernmost states of the conterminous USA over the period 1910-1998, finding that the long-term SWE trend of the region was negative, indicative of declining winter precipitation. In addition, they report that their results "reinforce more tenuous conclusions made by previous authors," citing Chagnon et al. (1993) and McCabe and Legates (1995), who studied snow course data from 1951-1985 and 1948-1987, respectively, at 275 and 311 sites, and who also found a decreasing trend in SWE at most sites in the Pacific Northwest.

Four years later, Julander and Bricco (2006) reported that snowpack data were being consistently used as indicators of global warming, and that it was thus essential that individuals doing so quantify, as best they could, all other influences imbedded in their data. That meeting this requirement is no trivial undertaking is indicated by their statement that "snow data may be impacted by site physical changes, vegetation changes, weather modification, pollution, sensor changes, changes in transportation or sampling date, comparisons of snow course to SNOTEL data, changes in measurement personnel or recreational and other factors," including sensors that "do not come back to zero at the end of the snow season." In an analysis of 134 sites (some having pertinent data stretching back to at least 1912), they thus selected fifteen long-term Utah snow courses representing complete elevational and geographic coverage of the dominant snowpacks within the state and adjusted them for the major known site conditions impacting the data, after which the adjusted data for the period 1990-2005 were "compared to earlier portions of the historic record to determine if there were statistically significant differences in snowpack characteristics, particularly those that could indicate the impacts of global warming."

Of the fifteen sites studied in greatest detail, the two researchers found that seven of them exhibited increased snowpack in recent years, while eight exhibited decreased snow accumulation. They also report that "six of the seven sites with increases have significant vegetative or physical conditions leading us to believe that the impacts associated with this analysis are overstated." The ultimate conclusion of Julander and Bricco, therefore, was that "any signature of global warming currently present in the snowpack data of Utah is not yet at a level of statistical significance ... and will likely be very difficult to isolate from other causes of snowpack decline."

Results that tell much the same type of story were obtained by Bartlett et al. (2005), who strove to determine what changes might have occurred in the mean onset date of snow and its yearly duration in North America over the period 1950-2002, based on data for the contiguous United States that come from the 1062 stations of the U.S. Historical Climatology Network, data for Canada that come from the 3785 stations of the Canadian Daily Climate Dataset, and data for Alaska that come from the 543 stations of the National Weather Service cooperative network in that state. As a result of their efforts, the three researchers found that "for the period 1961-1990 the mean snow onset date in North America [was] 15 December, with mean snow cover duration of 81 days." In addition, they report there were "no significant trends in either onset or duration from 1950 to 2002." Nevertheless, interannual variations of as much as 18 and 15 days in onset and duration, respectively, were present in the data; but for both parameters they report that "no net trend was observed."

We find it to be extremely interesting that from 1950 to 2002, during which time the air's CO2 concentration rose by fully 20% (from approximately 311 to 373 ppm), there was no net change in either the mean onset or duration of snow cover for the entire continent of North America; and to provide some context for this 62-ppm increase in atmospheric CO2 concentration, we note that it is essentially identical to the mean difference between the highs and lows of the three interglacials and glacials reported by Siegenthaler et al. (2005) for the period prior to 430,000 years ago. Surely, one would expect that such a change should have made some impact on North American snow cover, unless, of course, atmospheric CO2 enrichment has far less impact on climate than what climate alarmists claim it does.

In a somewhat different type of study, i.e., that of winter weather variability, which climate alarmists typically depict as becoming more extreme in response to global warming, Woodhouse (2003) generated a tree-ring based reconstruction of SWE for the Gunnison River basin of western Colorado that spans the period 1569-1999. This work revealed, in her words, that "the twentieth century is notable for several periods that lack [our italics] extreme years." Specifically, she reports that "the twentieth century is notable for several periods that contain few or no extreme years, for both low and high SWE extremes."

Also addressing the subject of extreme winter weather was Lawson (2003), who examined meteorological records for information pertaining to the occurrence and severity of blizzards within the Prairie Ecozone of western Canada. Over the period 1953-1997, no significant trends were found in central and eastern locations. However, there was a significant downward trend in blizzard frequency in the western prairies; and Lawson remarks 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 there "exhibit no trend in the severity of their individual weather elements." These findings, in his words, "serve to illustrate that the changes in extreme weather events anticipated under Climate Change may not always be for the worse."

Likewise concentrating on blizzards were Schwartz and Schmidlin (2002), who 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 for the conterminous United States. This effort resulted in a total of 438 blizzards being identified in the 41-year record, yielding an average of 10.7 blizzards per year; and linear regression analysis revealed a statistically significant increase in the annual number of blizzards during the 41-year period. However, the total area affected by blizzards each winter remained relatively constant; and if these observations are both correct, average blizzard size must have decreased over the four-decade period. On the other hand, as the researchers note, "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."

Yet another blizzard study was conducted by Changnon and Changnon (2006), who analyzed the spatial and temporal distributions of damaging snowstorms and their economic losses by means of property-casualty insurance data pertaining to "highly damaging storm events, classed as catastrophes by the insurance industry, during the 1949-2000 period." This work indicated, as they describe it, that "the incidence of storms peaked in the 1976-1985 period," but that snowstorm incidence "exhibited no up or down trend during 1949-2000." The two researchers thus concluded their paper by stating 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."

Last of all, Gulev et al. (2001) used sea level pressure taken from NCEP/NCAR reanalysis data for the period 1958-1999 to develop a Northern Hemispheric winter (January-March) climatology of cyclones (storms) that reached a sea level pressure of 1000 mb or lower. Linear trend estimates based on these data revealed a statistically significant (95% level) annual decline of 1.2 cyclones per year, suggesting that there were 50 fewer winter cyclones at the end of the study period than at its beginning. Additional analyses suggested that the Northern Hemisphere winter cyclones were intensifying at quicker rates and reaching greater maximum depths (lower sea level pressure) at the end of the record than they were at its beginning. However, the wintertime cyclones were also experiencing shorter life cycles at the end of the 42-year period, dissipating more quickly than at its beginning.

Could these changes be the result of global warming? According to the three scientists, they are probably connected to large-scale features of atmospheric variability, such as the North Atlantic Oscillation and the North Pacific Oscillation. As for the large decrease reported in the annual number of Northern Hemisphere cyclones over the 42-year period, we note that this observation is in direct opposition to climate-alarmist predictions, which suggest that the frequency of such events will increase as a result of global warming. Once again, therefore, the results of climate model simulations appear to be diametrically opposed to the testimony of nature.

In conclusion, snow and snowstorm data from North America provide no support for the climate-alarmist claims that (1) modern global warming did not commence until after 1910, (2) this warming has been primarily driven by anthropogenic greenhouse gas emissions, and (3) its continuance will lead to more frequent and more extreme weather phenomena, including windstorms and precipitation, which in winter equate to blizzards and snowfall. Real-world data just don't support their contentions.

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

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