September 21, 2014, by Tim Radford
Dark destroyer: a tornado tears through Kansas, one of the US states in ‘Tornado Alley’
Image: Goodland/US National Weather Service via Wikimedia Commons
Research showing that tornadoes are gradually forming earlier in the US could help states in the frontline to prepare better to withstand the storms’ devastating effects. LONDON, 21 September, 2014 − The terrifying whirlwinds that punctuate the mid-Western summer in the US so frequently as to earn the nickname “Tornado Alley” for the southern plains region states such as Nebraska, Kansas, Oklahoma and northern Texas are forming up to two weeks earlier than they did 60 years ago. John Long and Paul Stoy, research scientists at Montana State University, report in the journal Geophysical Research Letters that, on average, the tornado season advanced by one week between 1954 and 2009. For many states, the shift is almost 14 days. Peak activity on average used to occur on 26 May, but this century the peak has shifted to 19 May. On the plus side, the tornado season is also ending earlier than it did in the 1950s. Tornadoes happen in every continent except Antarctica, but particularly in America. There are on average around 1,300 in the US every year, and on average they kill about 60 people. They are graded according to the punch they pack: the Fujita scale of tornado rating ranges from F1, with winds at 117 kilometres per hour to 180 kph, to F5, at between 420 kph and 511 kph.
Increase in ferocity
Long and Stoy are not the first to note a change in the pattern of storms. Recently, researchers calculated that, overall, the number of tornadoes each year may be dwindling, but their ferocity seems to be on the increase. Some researchers think climate change is a factor, but the two Montana scientists are more cautious. They say it takes a mix of topography, temperature, wind patterns and other factors to set in motion the swarms of storms that can slam into a town and wreck tens of thousands of homes in a matter of minutes. “Observed climate trends cannot fully account for observations,” they say in the formal language demanded by science journals. But they also point out that if the tornado season is occurring earlier in the year, then it might help individuals, local authorities, emergency services and state governments to know this, and to be prepared. – Climate News Network
Tim Radford, a founding editor of Climate News Network, worked for The Guardian for 32 years, for most of that time as science editor. He has been covering climate change since 1988.