Background
The authors note that (1) "global climate models predict that more weather extremes will be a part of a changed climate due to greenhouse gases," that (2) such a climate change "is anticipated to result in alterations of cyclone activity over the Northern Hemisphere (Lawson, 2003)," and that (3) "a change in the frequency, locations, and/or intensity of extratropical cyclones in the mid-latitudes would alter the incidence of snowstorms [our italics]," citing the paper of Trenberth and Owen (1999). Hence, they decided to see if real-world data could shed any light on the veracity of this prediction.

What was done
In the words of the Changnons, "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." In support of this approach to the subject, they report that the National Academy of Sciences has identified insurance catastrophe data as "the nation's best available loss data (National Research Council, 1999)."

What was learned
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."

What it means
The two researchers conclude 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."

References
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.

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