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Tuesday, April 28, 2015
- High water temperatures in the North Atlantic Ocean and Caribbean Sea are the main reason behind this year’s unusually early and active hurricane season, which could be even more severe than was initially predicted, according to experts.
Cuba was already hit in early July by Hurricane Dennis, which caused 16 deaths and an estimated 1.4 billion dollars in damages, and the chances of more hurricanes striking this year are high, said Maritza Ballester Pérez, a researcher at the Cuban Meteorology Institute Forecast Centre.
The number of tropical storms predicted to pass through the region during this year’s hurricane season, which runs from Jun. 1 to Nov. 30, has risen from 13 to 20, she told IPS.
And according to the new, updated forecast issued Aug. 1, nine of these tropical storms could develop into full-blown hurricanes.
The new Cuban forecast is similar to the 2005 Atlantic Hurricane Season Outlook released by the U.S. government’s National Oceanic and Atmospheric Administration (NOAA), which was also modified on Aug. 2 to reflect an even more active season than previously expected.
The NOAA is now forecasting a total of 18 to 21 tropical storms and nine to 11 hurricanes, up from the 12 to 15 tropical storms and seven to nine hurricanes it had predicted in May.
“The fundamental cause of this activity lies in the high sea temperatures observed throughout the North Atlantic and the Caribbean Sea,” said the head of the Cuban Meteorology Institute Climate Centre, Ramón Pérez Suárez.
Tropical storm and hurricane are terms used in the North Atlantic and Caribbean for what is known generically as a tropical cyclone (called a typhoon in the Pacific).
Tropical cyclones are large, rotating areas of clouds, wind and thunderstorm activity which form over the sea in the presence of certain variables, including sea surface temperatures above 26.5 degrees Celsius and upper level atmospheric conditions conducive to thunderstorm formation.
Sea surface temperatures in the western Caribbean Sea have reached 30 to 31 degrees, according to figures released in July by the head of the Cuban Meteorology Institute Forecast Centre, José Rubiera.
Pérez Suárez told IPS that in April, May and June, surface temperatures in both the Caribbean Sea and the North Atlantic Ocean were the highest since 1951.
And in the North Atlantic, he added, these unusually high temperatures have been observed since the second half of 2004.
But Pérez Suárez is cautious when it comes to attributing higher sea surface temperatures and the increase in the frequency and intensity of tropical storms and hurricanes to climate changes brought about by global warming.
“We cannot completely rule out the possibility that the increase we are now observing could be partially a consequence of climate change, but at least for the moment, there is no firm proof of it,” he commented.
A growing number of scientists, however, believe that the build-up of “greenhouse gases” like carbon dioxide, methane and nitrous oxide, which trap the sun’s heat in the earth’s atmosphere, is responsible for the more frequent and intense extreme weather phenomena observed in recent years.
To confront the threat posed by global warming, the Kyoto Protocol, which entered into force in February, commits the industrialised countries that have ratified it to reducing their greenhouse gas emissions to volumes 5.2 percent lower than 1990 levels, by a deadline of 2012.
A large part of the harmful greenhouse gases released into the atmosphere result from the burning of fossil fuels like oil, gas and coal in industry and transportation.
Although it is the world’s largest producer of greenhouse gases, accounting for one-forth of global emissions, the United States has not only refused to ratify the Kyoto Protocol, but actually withdrew its signature, on the grounds of the potential harm to its national economy.
U.S. expert Kerry Emanuel of the Massachusetts Institute of Technology (MIT) noted in a recent study that the average sea surface temperature has increased by one degree since 1970.
“My results suggest that future warming may lead to an upward trend in tropical cyclone destructive potential,” he added.
Other experts maintain that the greater frequency and intensity of tropical storms and hurricanes in the North Atlantic over recent years is the result of a natural cycle in the region that repeats every few decades.
Pérez Suárez noted that the most active hurricane season in recorded history in the North Atlantic occurred in 1933, with a total of 21 tropical storms, while there were 18 tropical storms in 1969 and 19 in 1995.
“The causes for these increases have been linked to a rise in sea temperature and variations in atmospheric circulation, similar to what is being observed now,” he added.
Up until July, of the seven tropical storms that have formed so far this year in the region encompassing Central America, the Caribbean, Mexico and the southeastern United States, two developed into destructive hurricanes, Dennis and Emily.
The first two months of this year’s hurricane season were even more active than the same period in 1933 and 1995, the most active overall in recorded history.
Beginning in 1996, and particularly since 2001, there has been a notable increase in tropical cyclone activity, observed Pérez Suárez.
Tropical cyclones are classified in accordance with maximum sustained wind speed into tropical depressions (up to 62 km an hour), tropical storms (between 63 and 117 km an hour) and hurricanes (118 km an hour or more). Once they have reached the category of a tropical storm, they are officially given a name.
Hurricanes in turn are classified according to the Saffir-Simpson scale, which ranges through category 1 (maximum sustained winds from 118 to 153 km an hour), 2 (154 to 177), 3 (178 to 209), 4 (210 to 250) and category 5 (over 250 km an hour).