Stronger storms not a product of global warming, says scientist
Global warming does not lead to more powerful typhoons, a Hong Kong scientist has controversially concluded after an intensive study of centuries of records.
Furthermore, City University of Hong Kong atmospheric scientist Johnny Chan Chung-leung is baffled by a sharp decline in the number of severe tropical storms entering the South China Sea.
Many weather experts believed a correlation existed between rising temperatures and the intensity of tropical storms. Although they could not statistically prove the hypothesis due to a lack of reliable data, many computer forecasting models backed their assertions.
After studying the number and strength of storms in the Pacific Ocean over the past few decades, and more than 500 years of government records in Guangdong province, though, Professor Chan has concluded, for now, that higher temperatures do not generate more intense storms.
'Global warming does not contribute to an increase in the intensity of tropical cyclones,' Professor Chan told the Sunday Morning Post. Global warming, the increase in the average temperature of the Earth's surface, is partly blamed on greenhouse gases produced by man-made air pollution. While there is no dispute among scientists that temperatures are steadily rising, there is disagreement about how they affect events like severe tropical storms.
Australian researcher Penny Whetton, the leader of the Commonwealth Scientific and Industrial Research Organisation's climatic impact team, said temperatures had risen noticeably, especially in the past 50 years. Trends were not that discernible when it came to other aspects of climate, particularly the frequency of extreme events, she acknowledged.
'For extreme events in particular regions, we usually find that the natural fluctuations are too strong to be able to say something firm about whether greenhouse gases are already affecting that system,' Dr Whetton said from Melbourne. 'If the results don't show anything particularly unusual happening ... I don't think it proves anything one way or the other.'
Ocean temperatures must be at least 27 degrees Celsius for tropical storms to develop, and some models show that as temperatures rise due to global warming, the likelihood of more severe storms also increases. The staunchest exponent of the view is American hurricane expert Kerry Emanuel, based at the Massachusetts Institute of Technology.
While he admitted last week that his belief was still a theory and climate models gave conflicting indications, he predicted the severest storms were likely to be fiercer with a significant rise in temperatures.
'If the ocean temperature goes up 2 degrees in the tropics, then the maximum wind speeds in the fiercest hurricanes could go up by 24 to 32km/h, from 240 to 264km/h. And that's noticeable,' he said.
Professor Chan's research rejected such a notion, although he was concerned his view was being swamped by proponents of Professor Emanuel's view. A study he recently submitted to a prestigious international journal rejecting the theory was determined to be 'politically incorrect', he claimed.
His research had found that while Pacific Ocean temperatures had risen about half a degree, to 29 degrees, over the past 40 years, there had been no corresponding rise in the strength of typhoons. In fact, the opposite trend was observed.
Noticeable, though, was that a third fewer typhoons were coming into the South China Sea than 30 years ago. 'We think it is something to do with the ocean currents,' he said.
