admin /22 September, 2006
A group of climate scientists published a major study on 18 September that "closes the loop" on the connection between hurricanes and climate change, according to the Inter Press Service news agency.
Jump in hurricane power "startling": "There is no doubt at all that hurricane intensity has increased," said Kerry Emanuel, a climatologist at the Massachusetts Institute of Technology, one of the 19 scientists who published the findings in the Proceedings of the National Academy of Sciences (PNAS). "I was startled to see the power of hurricanes and cyclones increase by 50 to 100 percent since the 1970s."
Slight warming has big impact: Sea surface temperatures in the regions around the equator where hurricanes and cyclones are born had increased about 0.5 C since 1970. That relatively small rise was the main factor in observed increases in storm intensity. It turned out that hurricanes were more sensitive to increased sea surface temperatures (SST) than previously believed, Emanuel said
Discussion declared over: "That has us all worried," he added. There had been substantial, sometimes acrimonious debate about the connection between global warming and the increase in the number and strength of hurricanes over the past 10 to 15 years. That debate is now over, based on the PNAS study, which documented a clear link to rising SST in the regions of the Atlantic and Pacific Oceans that give birth to hurricanes.
Fiercest storms double in number: That study and other recent scientific research close the loop on the link between human-induced climate change and hurricanes, said Robert Corell of the American Meteorological Society. "The number of most powerful storms, Category 4 and 5, have nearly doubled in the past 35 years."
Much of Atlantic affected: "The regions of the oceans where hurricanes and cyclones are born have seen substantial increases in the sea surface temperatures," Corell said in an interview. Those SST increases have affected large parts of the Atlantic Ocean, so that the number of hurricanes have increased as well as their intensity, said Greg Holland, a climatologist and divisional director of the National Centre for Atmospheric Research.
Shifts 70pc due to climate change: Although natural variability plays a part in the increase in numbers and intensity, the impact of climate change is the predominant factor, said Holland. "The changes we’re seeing in the North Atlantic are 70 percent due to climate change effects."
Human emissions the only explanation: To reach these conclusions, researchers started with actual SST and storm measurements using satellites, ocean buoys and other data. Then, using 22 different computerised climate change models, they determined that human emissions were the only explanation for the observed rise in SST. Ocean temperatures would continue to climb higher, all of the models showed.
Storm dynamics defy predictions: Although the 0.5 C rise in SST since the 1970s produced a dramatic 50 to 100 percent increase in storm intensity, the dynamics of hurricanes are too complex to extrapolate about what kinds of storms will be produced by warmer seas, said Emanuel.
Reference: World Business Council for Sustainable Development, website: www.wbcsd.org
Erisk Net, 19/9/2006