Fewer cyclones, but more intense: study
Tropical cyclones may become less frequent this century but pack a stronger punch as a result of global warming, according to a new paper.
The study, which appears in the journal Nature Geoscience, is an overview of work into one of the more extreme yet least understood aspects of climate change.
Known in the Atlantic as hurricanes and in eastern Asia as typhoons, tropical storms are driven by warm seas, which raises the question about what may happen when temperatures rise as a result of increasing levels of greenhouse gases.
Dr Tom Knutson and colleagues from the UN's World Meteorological Organisation (WMO) looked at peer-reviewed investigations that have appeared over the past four years.
Their benchmark for warming is the 'A1B' scenario, a middle-of-the-road computer simulation which predicts a global average surface temperature rise of 2.8°C over the 21st century.
"It is likely that the global frequency of tropical cyclones will either decrease or remain essentially unchanged," says the paper.
But storms could have more powerful winds - an increase of between 2% and 11% - and dump more water, it warns.
Rainfall could increase by 20% within 100 kilometres of the eye of the storm.
In addition, some storm basins will "more likely than not" see a big increase in the frequency of high-impact storms.
More research needed
The overview calls for an effort to fill in some big gaps in knowledge, including the variability of cyclones in the past and how global warming will affect storm behaviour in specific regions.
The findings broadly concur with those of the UN's panel of climate scientists, which in a 2007 report says it was "likely" that tropical cyclones would become more intense this century, with heavier rainfall and stronger wind speeds.
However, the panel says it is less confident in concluding whether the number of cyclones would decrease.