Sea surface warming contributes to increased hurricane activities

2008-01-31 19:17:36 Xinhua English

LONDON, Jan. 31 (Xinhua) -- Researchers from the University College London (UCL) have found that local sea surface warming was responsible for around 40 percent of the rise in number of storms between 1996 and 2005 in the North Atlantic, compared with the 1950-2000 average.

According to a report published in Nature Thursday, it is the first time that scientists have quantified the contribution of sea warming to the increased hurricane activities.

The number of North Atlantic hurricanes has been above normal in nine of the last 11 years, reaching a peak in 2005, when 15 hurricanes formed between June and December, the magazine said.

Mark Saunders and Adam Lea of the UCL used a statistical model to disentangle the two main hurricane predictors -- sea surface temperature and near-surface trade wind speed.

These two variables together explain about 80 percent of the variance observed in tropical Atlantic hurricane activities between 1965 and 2005.

Their result indicates that a 0.5-degree-Celsius increase in August-September sea surface temperature could result in an average 40 percent increase in hurricane activities, including both number and severity of storms.

In the tropical North Atlantic, sea surface temperatures in the1996-2005 period were 0.27 degree Celsius above average, the highest ten-year anomaly since records began in 1950.

Computer models suggest that sea surface temperatures in the Atlantic hurricane-forming region could warm by two degrees Celsius by 2100.

If this happens, maximum wind speeds of hurricanes could increase by 63 percent, with damage from hurricanes rising in proportion to the cube of the wind speed.

The warmer the water, the more moisture and energy is available for intense storms to develop, the study showed.

However, the proportion of storms that hit the land versus those that stay at the sea is unlikely to change, but the area of ocean surface warm enough to form hurricanes is likely to expand, making more coastline susceptible to these storms, the report said.