WASHINGTON (AFP) -- Global warming's effect on wind patterns and sea temperatures have nearly doubled the number of hurricanes a year in the Atlantic Ocean over the past century, says a new study by U.S. scientists.

Excerpts from the study by Greg Holland of the National Center for Atmospheric Research and Peter Webster of Georgia Institute of Technology were released in the United States late Sunday.
The analysis identifies three periods since 1900, during which the average number of hurricanes and tropical storms increased 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 -- the next category down.
From 1930 to 1940, the authors point out, 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 stabilized, 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