Atlantic Cyclones May Decrease As Globe Warms - Study
The study, published on Sunday in Nature Geoscience, adds fuel to a fierce scientific debate over whether human-produced greenhouse gases have contributed to a recent rise in hurricane activity in the Atlantic basin and whether tropical cyclones are becoming stronger.
A simulation of Atlantic hurricane activity for the final decades of the century projected an 18 percent decrease in hurricanes and a 27 percent decrease in tropical storms, researchers at the
"It does not support the notion that increasing greenhouse gases are causing a large increase in Atlantic hurricane or tropical storm frequency," said Thomas Knutson, one of the study's authors.
Recent studies have found links between rising sea surface temperatures in the tropical
Around 1995, scientists believe, the
The frenzied hurricane seasons of 2004, when four strong hurricanes hit
The next six-month Atlantic hurricane season begins on June 1 and
forecasters expect it to be a busy one, well above the long-term average season that produces about 10 tropical storms and six hurricanes.
A well-known forecasting team at
Forecasters have been wrong in the last few years.
Global energy, commodities and insurance markets have paid close attention since 2004 and 2005, when the steady stream of Atlantic storms -- including $80 billion in damage from Hurricane Katrina -- marched through US oil and gas fields in the Gulf of Mexico.
WIND SHEAR RISING
The study by the Geophysical Fluid Dynamics Laboratory used a global warming scenario for the rest of the century projected by the UN Intergovernmental Panel on Climate Change.
That included a rise of 1.7 degrees Celsius in Atlantic sea temperatures, higher vertical wind shear and lower low- to mid-tropospheric humidity across the
Researchers said water temperatures in the tropical
"Now those models could be wrong ... (but) without that rapid increase in the Atlantic compared to the other tropical basins, our models do not expect a rapid increase in Atlantic storminess," said researcher Isaac Held.
Vertical wind shear, a difference in wind speeds at varying altitudes that tends to tear apart nascent hurricanes, could be another contributor. Researchers said the environment may become more hostile to cyclones before the end of the century.
"We've had lower levels of vertical wind shear (in recent years), but the climate model projections are not indicating reduced wind shear in the Atlantic but rather ... increased vertical wind shear," Knutson said.
The model projects more rainfall from hurricanes toward the end of the century and a modest increase in intensity.
Knutson said a past study forecast a 4 percent rise in intensity for every 1 degree C rise in sea temperature, but this latest study found a smaller rise of 1 to 2 percent.
The researchers said their findings for the Atlantic basin would not necessarily apply to other ocean basins, in part because wind shear was not expected to rise elsewhere.
Noting the debate among hurricane and climate researchers on the issue of global warming and hurricanes, Knutson said: "We don't regard this as the last word on this topic."