November 7, 2006

No Ramp-Up in Damaging Snowstorms

Filed under: Precipitation

Global climate models – the complex quantitative representations of Earth’s atmosphere and its interaction with the planet’s land masses and ocean bodies – have portrayed a future climate that is riddled with ferocious weather. Super hurricanes, more frequent and intense drought, flooding precipitation events, and unimaginable severe weather outbreaks lead the cast of villains that will supposedly be engineered by increased greenhouse gases in Earth’s atmosphere. An exaggerated image of a global climate gone mad is a wonderfully effective tool for climate change alarmists. Historically, severe weather has been an intrigue, as evidenced by the massive media coverage of events either in anticipation or in retrospection. Natural hazards can be viewed with guilt-free sympathy, as they are indeed natural and leave no one to blame. Incorporate weather extremes in the global warming debate and there exists an opportunity to indeed assign blame and make severe weather events less innocent. It’s the age-old strategy of making the public afraid of something before telling them who is to blame for it.

One form of extreme weather that gets little play by climate change alarmists is hazardous snowstorms. This is probably because the image of increased snow detracts from their portrait of a warmer climate. However, the increase in extreme weather predicted by global climate models “is anticipated to result in alterations of cyclone activity over the Northern Hemisphere” (Lawson, 2003), and that “a change in the frequency, locations, and/or intensity of extratropical cyclones in the mid-latitudes would alter the incidence of snowstorms” (Trenberth and Owen, 1999). In a recent article in the journal Natural Hazards, snowstorm data over the last half of the 20th century were analyzed in search of support for this theory.

“A spatial and temporal analysis of damaging snowstorms in the United States” reports on the work of the father-and-son research team of Stanley and David Changnon, who examined “damaging” snowstorms across the country over the period 1949 through 2000. The Changnons defined damaging snowstorms as those causing more than $25 million in property losses using property-casualty insurance data that consist of highly damaging storm events of all types that are classified as catastrophes by the insurance industry. Their use of the data is defended by the contention of the National Academy of Sciences that insurance catastrophe data is the nation’s best available loss data.

A total of 155 damaging snowstorms formed a subset of the catastrophes data base. The authors note that snowstorms are a problem in almost all regions of the United States. However, nearly one-half occurred in the northeastern portion of the country and another 34% occurred in the central portion of the United States. The southeastern region also experienced a significant number of storms, while the west experienced the least, partially owing to a smaller population density in the western areas susceptible to snowstorms.

Shifts in the minimal selection criteria used by the insurance industry for storm reporting produced a temporal bias in the catastrophe data base when using $25 million to define storms as “damaging.” Analysis of the data base in previous research indicated that catastrophes causing losses of $35 million dollars or greater lend themselves to an unbiased study of long-term trends. As such, the authors adopted that criterion to define “severe” snowstorms, yielding 100 events from the 52-year study period. Two periods of a high frequency of damaging snowstorms were evident in the database: 35 events during the period 1956 through 1965 and 41 events from 1976 through 1985. The two periods with the lowest frequency of events were 1971 through 1975 and 1991 through 1995. The average number of severe snowstorms over the first 32 years of the study period was 3.2 per year, while the average over the 20-year period of 1981 through 2000 was notably less at 2.7 per year. However, the authors report that the frequency of damaging snowstorms across the United States was characterized by “no upward or downward trend” across the 52-year study period (Figure 1). On the other hand, national monetary losses did show a significant upward trend through the period, and the authors conclude that this indicates “a growing societal vulnerability to snowstorms” rather than an increase in their frequency. So it seems that American society has become increasingly vulnerable to snowstorms while the climatology of snow storms has not changed.


Figure 1. The frequency of severe storms (> $35 million in losses; year 2000 dollars) and the amount of losses for 4-year periods during 1949-2000. (Taken from Changnon and Changnon, 2006).

Forecasts of a future climate with increasingly ferocious weather events make for great science fiction movies and dramatic public rhetoric. The incidence of snowstorms in the middle latitudes is included in the cast of weather phenomena that are predicted to become nastier, and it would seem that evidence in support of this theory could be seen in data from the last few decades of the 20th century. However, the work of Stanley and David Changnon reveals no such evidence, as they conclude: “The temporal frequency of damaging snowstorms during 1949–2000 in the U.S. 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:

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

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

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




No Comments

No comments yet.

RSS feed for comments on this post.

Sorry, the comment form is closed at this time.

Powered by WordPress