Background
The authors report that snowpack data are being consistently used as indicators of global warming, and that it is thus essential that individuals doing so quantify, as best they can, all other influences imbedded in the data. That this 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."

What was done
Out of a total of 134 sites, some having pertinent data stretching back to at least 1912, fifteen long-term Utah snow courses "representing complete elevational and geographic coverage of the dominant snowacks within the state were analyzed and adjusted for the major known site conditions impacting the data," after which the adjusted data (1990-2005) were "compared to earlier portions of the historic record to determine if there were statistically significant differences in snow pack characteristics, particularly those that could indicate the impacts of global warming."

What was learned
Of the fifteen sites studied in greatest detail, Julander and Bricco 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." In addition, they say that "when looking at those sites that are accumulating less snow in the adjusted data and those that would theoretically show the impacts of global warming first, none are statistically different either in the adjusted data or the non-adjusted data."

What it means
The ultimate conclusion of the two U.S. Department of Agriculture researchers 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."