Wild, wacky weather and global warming

A tornado ripped through northwest Connecticut on Wednesday, touching down four times and in the process hit the towns of East Litchfield, Thomaston, Terryville and Bristol, according to the National Weather Service. The storm took with it large, stately old trees, damaged homes and frayed nerves, but fortunately caused no death or injuries.

The event follows another tornado hit on June 24 that caused extensive damage in Bridgeport. That unwanted urban invader ripped off roofs, knocked down buildings, toppled trees and shattered windows in the densely developed city.

Those tornadic events are the most dramatic exhibits for what has been an unusually warm, oppressive and stormy summer. Severe thunderstorm watches and warnings, sprinkled occasionally with tornado watches, have become regular occurrences. But no matter how frequently the storms strike, they have only applied temporary relief, if any, from the high temperatures and humidity.

It all seems out of place for normally placid southern New England. Is it evidence of weather havoc caused by global warming?

Maybe, but maybe not.

An isolated hot, stormy summer is no more convincing evidence of global warming than a series of winter snowstorms are proof of global cooling. For better evidence scientists look for long-term trends and there the substantiation of a warming Earth is stronger.

An analysis of global surface temperatures by NASA scientists found that 2009 was tied for the second warmest year since 1880. And in the Southern Hemisphere, the past year was the warmest on record. Meanwhile, January 2000 to December 2009 was the warmest decade on record. Looking back to 1880, when modern scientific instrumentation became available to monitor temperatures precisely, a clear warming trend is present, say NASA scientists. Average global temperatures have increased by about 1.5 degrees Fahrenheit since 1880. That seemingly small number is actually dramatic climatologically.

As for tornadoes, while unusual, they are hardly unheard of in Connecticut. Since good tornado record keeping began in 1950, weather observers have documented more than 100 tornadoes in the state, according to the National Climatic Data Center.

What is the busiest month for tornadoes in Connecticut? August. Stay tuned to those weather alerts.