July 31, 2007	Tuesday	Rajab 15, 1428

WASHINGTON: Global warming’s effect on wind patterns and sea temperatures have more than doubled the annual number of hurricanes in the Atlantic Ocean over the past century, says a new study by US scientists.

Excerpts from the study by Greg Holland of the National Centre for Atmospheric Research and Peter Webster of Georgia Institute of Technology were released in the United States late on Sunday.

The analysis identifies three periods since 1900, during which the average number of hurricanes and tropical storms surged dramatically and then remained elevated and relatively steady.

The first period, between 1900 and 1930, saw an average of six Atlantic tropical cyclones, of which four were hurricanes and two were tropical storms.

From 1930 to 1940, the annual average increased to 10, consisting of five hurricanes and five tropical storms.

In the most recent period, from 1995 to 2005, the average reached 15, of which eight were hurricanes and seven were tropical storms.

This latter period, Holland and Webster caution, has not yet stabilised, which means the average hurricane season may be more active in the future.

“These numbers are a strong indication that climate change is a major factor in the increasing number of Atlantic hurricanes,” Holland said in a statement.

The scientists see a strong correlation between the spike in storm activity and rising sea surface temperatures, which “feed” hurricanes.

Over the last 100 years, these temperatures have risen by about 0.7 degrees Celsius, the study asserts.

The temperatures rose approximately 0.4 degrees Celsius, in a period leading up to 1930, which was marked by some of the deadliest storms to hit the Atlantic Coast of the United States.

The so-called Galveston hurricane of 1900 that went down in history as the worst ever to hit the United States, took an estimated 8,000 lives.

The second-worst storm that ravaged south-eastern Florida and killed about 2,500 local residents occurred in 1928, according to data compiled by the National Hurricane Centre.

Another hurricane that hit the Miami area in 1926 caused 372 deaths, a 1919 storm in the Florida Keys was responsible for 287 fatalities, and an unnamed category four hurricane that befell New Orleans in 1915 took 275 lives. A similar water temperature rise, according to the study, was recorded leading up to 1995.

The second-costliest US Atlantic hurricane, Andrew, hit Florida and Louisiana in 1992 causing $26.5 billion in damages.

Katrina, the costliest and third-deadliest US Atlantic storm, which killed about 1,500 people and caused $81 billion in damage, ravaged the states of Louisiana and Mississippi in 2005.

Critics of the global warming theory have often held that data showing increased hurricane activity account for better observation rather than changing global weather patterns.

But Holland and Webster refute these assertions, arguing that the distinct transitions in hurricane activity noted by the study occurred around 1930 and 1995, while aerial and satellite observation of hurricanes stated respectively in 1944 and in 1970.

“We are of the strong and considered opinion that data errors alone cannot explain the sharp, high-amplitude transitions between the climatic regimes, each with an increase of around 50 per cent in cyclone and hurricane numbers, and their close relationship with” sea surface temperatures, the authors state.—AFP