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Monday, 30 January 2006: 12:40 PM
Stanley Changnon, Changnon Climatologist, Mahomet, IL

Most persons react negatively when asked about the impacts of thunderstorms. Traditionally, thunderstorms are viewed as dangerous and deadly. The curse of thunderstorms includes their heavy rains and high rainfall rates which produce sizable soil erosion and deadly and very damaging flash floods. Lightning is a second curse causing fires and deaths to humans, with an average of 144 deaths per year in U.S., second only to deaths from heat waves. High winds generated by storm downdrafts cause property and crop damage, and hail, a product of many storms, is a major damage producer to U.S. crops and property. Last but not least are tornadoes, another phenomenon generated mainly by thunderstorms. Assessment of the nation's insured crop and property losses over the 1950-2000 period revealed storms, lightning, and their heavy rains caused an average loss of $3.814 billion per year. Storm-generated high winds average annual losses were $168 million, and hail produced $444 million in losses, and tornadoes produce losses averaging $458 million annually. The total annual insured losses from thunderstorms in the U.S., in 2000 dollars, is $4.874 billion. Insured losses represent about 80 percent of all losses and application of this adjustment brings the nation's average loss from thunderstorms to $6.1 billion yearly.

Few stop to realize that thunderstorms, like most damaging weather phenomena, also produce sizable benefits to the environment and economy. Thunderstorms are essential to the environment and society, and one of their major blessings is the production of copious rainfall worth billions of dollars to the nation's economy. Storms account for 47% of all precipitation east of the Rockies and 70% in southwestern U.S. The absence of thunderstorms, such as in the summer of 2005 in Illinois, led to $2 billion in crop losses and is often a key factor in droughts. Lightning converts gaseous nitrogen into compounds essential to plants, and lightning fixation accounts for 20% of the global total nitrogen deposited. Storms also maintain the global electrical circuit, transferring electrical charge from the atmosphere to the earth. Thunderstorms also play a significant role in the atmosphere's chemistry with updrafts transporting pollutants aloft and storm rainfall scavenging vast amounts of pollutants in the air.