Climate Change, Environment, Global, Global Geopolitics, Headlines

ENVIRONMENT: New Data Erases Doubt on Storms and Warming

Stephen Leahy

BROOKLIN, Canada, Sep 11 2006 (IPS) - There is little doubt now that climate change is making hurricanes and cyclones much more powerful and more frequent, top scientists announced Monday.

Sea surface temperatures are rising due to global warming and more than a dozen studies since Hurricane Katrina hit the United States last August show this has resulted in the dramatic increase in the strength of hurricanes in recent years.

“There is no doubt at all that hurricane intensity has increased,” said Kerry Emanuel, a climatologist at the Massachusetts Institute of Technology.

“I was startled to see the power of hurricanes and cyclones increase by 50 to 100 percent since the 1970s,” said Emanuel, one of 19 climate scientists who published a major study Monday in the Proceedings of the National Academy of Sciences (PNAS).

Sea surface temperatures in the regions around the equator where hurricanes and cyclones are born have increased about 0.5 C since 1970. That relatively small rise is the main factor in the observed increases in storm intensity.

It turns out that hurricanes are more sensitive to increased sea surface temperatures (SST) than previously believed, Emanuel told IPS. “That has us all worried,” he added.

There has been substantial and sometimes acrimonious debate about the connection between global warming and the documented 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 documents a clear link to rising SST in the regions of the Atlantic and Pacific Oceans that give birth to hurricanes.

The PNAS paper and other recent scientific research close the loop on the link between human-induced climate change and hurricanes, says 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,” Corell told IPS.

Hurricane strength is measured by the Saffir-Simpson Hurricane Scale, which categorises storms between one and five depending on their sustained wind speeds. Intensity refers to the total dissipation power over the lifetime of a storm. It should be noted that the majority of all hurricanes or cyclones never make landfall.

“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, says Greg Holland, a climatologist and divisional director of the National Centre for Atmospheric Research.

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,” he said.

And it is emissions from the burning of fossil fuels and deforestation that is resulting in these climate changes, the PNAS study makes clear.

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.

Although the computer models were created by various climate research centres around the world, there was “exceptional correlation that human-induced climate change was the only way to get those SST results”, said Tom Wigley a climate scientist at the National Centre for Atmospheric Research and a co-author of the PNAS paper.

These are the latest computer models and researchers have a high level of confidence in their results, says Wigley. “There is less than a one percent chance that the changes in SST could be the result of non-human factors,” he said.

Ocean temperatures will continue to climb higher all of the models show. “The current rise in SST is small beans compared to what we will see in the future,” Wigley noted.

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 make an extrapolation about what kinds of storms will be produced by warmer seas, says Emanuel.

When it comes to hurricanes, the United States has a more immediate problem, he says.

“The U.S. has a very big societal problem when it comes to coping with hurricanes,” Emanuel said. “The threat hurricanes pose has to taken more seriously.”

FEMA, the federal disaster management and assistance agency, and hurricane insurance among other things need to be addressed properly, he said.