Global warming 'not linked' to typhoons

Telegraph, November 7, 2007

By Roger Highfield, Science Editor

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A study of intense typhoons in the Pacific has failed to show a link with global warming, instead revealing that their number waxes and wanes naturally over the decades.

Even in the Atlantic, where these intense storms are called hurricanes, climate experts have not formed a consensus, with many - but by no means all - believing hurricanes have become stronger and longer-lasting over the past 30 years due to a rise in sea surface temperatures, possibly as a result of global warming.

Today, in the Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, a study of typhoons is published by Prof Johnny Chan, City University of Hong Kong.

A major conclusion of his study is that global warming apparently is not related to the frequency of intense typhoons.

Instead, such occurrences have a strong decadal variation caused by similar variations in the oceanographic and atmospheric conditions that govern the formation, intensification and movement of tropical cyclones.

Prof Chan said that there are key differences between the Pacific and the Atlantic. In the latter, sea-surface temperature is generally close to a threshold of 27 degrees, beyond which more tropical cyclones are more likely to form, he said.

Although some have linked hurricanes to climate change, others believe the variations follow a natural cycle, he said: "More analyses are necessary before one can say one way or the other."

For the western North Pacific, the sea surface temperature is always above the threshold. "Therefore, a slight increase due to global warming would not have a great influence".