ARE the most powerful, devastating hurricanes becoming the norm? Hurricane researchers are divided over the issue. When hurricane Dean reached category 5 strength in the Caribbean on Monday night, 2007 became the fourth year out of the past five to host the most intense category of storm 鈥� an unparalleled record.
鈥淲e鈥檙e in transition now to a new regime,鈥� with warmer sea-surface temperatures fuelling more and stronger storms, says Peter Webster of the Georgia Institute of Technology in Atlanta, who has reported both that hurricanes are becoming more intense and that storm frequency in the North Atlantic began to rise significantly in 1995 (Science, ).
Category 5 storms have been uncommon: during 43 of the seasons since 1940, no such storms were recorded. The only time before now that a category 5 storm has been recorded during three out four years was between 1958 and 1961.
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Other hurricane specialists are sceptical of Webster鈥檚 conclusions, however, claiming that previous storm records were badly collated and based on flawed observations. We don鈥檛 truly know the extent of past hurricanes, says Kerry Emmanuel of the Massachusetts Institute of Technology: 鈥淚t鈥檚 hard to tell.鈥� Aircraft observations began in the 1940s, but Emmanuel says that for a decade 鈥渢hey just guessed wind speeds by looking at the water鈥�. Early hurricane-hunter planes weren鈥檛 strong enough to fly into the eye of a fierce storm, and satellite observations didn鈥檛 start until 1965.
Today鈥檚 observations can even spot high winds over the open ocean that would have been missed before, says Chris Landsea of the National Hurricane Center in Miami, Florida. 鈥�Hurricane Wilma in 2005 was category 5 for 18 hours, but in the 1950s all we would have known was that it was category 4 when it hit Cancun,鈥� he told New 杏吧原创.
鈥淭oday鈥檚 observations spot high winds over oceans that would have been missed before鈥�
