Andrew Dlugolecki, a former insurance executive who wrote a report on the "changing climate" of the industry last year for the Assn. of British Insurers, said that companies could profit from awareness of the issue. But he said that unless insurers could adjust their premiums to match the uncertainties they see, they eventually might stop offering some types of coverage, such as insurance to oceanfront properties that might be vulnerable to rising sea levels.
"The real issue is that some things may become uninsurable in the future, which would become a big problem for other industries, including the financial industry," Dlugolecki said. "They want to provide loans on the basis that property losses will be insured. If those losses are not going to be insured, they may not want to provide the loans."
Although many European insurers have become believers in climate change and have begun advocating for reductions in greenhouse gases to offset the possible effects, American companies generally have adopted a wait-and-see stance. The contrast, insurance experts said, reflects the differences in the way global warming is regarded by politicians and the public on the two sides of the Atlantic.
Fid Norton, a Harvard-trained scientist who works as a risk manager for GE Insurance Solutions in Kansas City, Mo., says he closely monitors research on global warming. But he remains unconvinced that it has played any role in the rise in insurance losses.
"We recognize what science is saying, but think it is premature to draw any quantitative conclusions about climate changes and issues such as hurricane frequency and intensity," he said.
Most hurricane experts agree. Although global warming theoretically could lead to stronger and more common storms, all events to date in the U.S. -- including the succession of hurricanes that hit Florida last year -- have a precedent in the last 150 years. Four hurricanes also made landfall in the U.S. in 1985.
"If you try to drive up someone's rates based on climate change, they will surely ask, what can you show me in the historical record to justify the statement that climate change is a proven threat?" said Rick Murnane, manager of the Risk Prediction Initiative, a hurricane research venture funded by insurers in Bermuda. "The climate change models are simply not good enough to be believed."
Attempts to connect recent hurricane activity to climate change have riled some hurricane scientists, who complain that environmental groups, insurance companies and even some fellow scientists have made unsupported claims.
"If you believe in climate change and its impacts, you tend to label everything an outgrowth of climate change," said Robert Muir-Wood, chief research officer of Risk Management Solutions, a consulting firm that employs more than 100 engineers and scientists to develop computer models on the risks of terrorism and natural disasters. "That tends to make me -- a fairly skeptical scientist -- a little irate."
But Muir-Wood, along with many other scientists, believes the 2003 heat wave that helped cause more than 20,000 deaths in Europe may have been a manifestation of climate change.
That summer, believed to be the hottest to hit Europe in half a millennium, also triggered forest fires and crop losses and led some insurers to conclude that global warming may have more ramifications than they realized.
At Harvard University's Center for Health and the Global Environment, scientists funded by Swiss Re are studying how rising temperatures could spread diseases such as West Nile virus and allergens such as ragweed pollen, driving up costs for the health and life insurance industries.
They also are examining whether ecosystem changes caused by warming could have major economic effects -- how collapsing coral reefs could leave oceanfront hotels prone to damage from tidal waves, for example, while bark beetle infestations could turn timberlands into tinderboxes.
Extreme weather may be the most sensational consequence of global warming, but scientists say that for insurers, it may not be the worst. Sudden changes caused by global warming, such as disease and pestilence, could have more long-lasting effect.
"We have not really appreciated how climate change could have some of these effects," said Paul R. Epstein, the Harvard Medical School instructor heading the study. "It may sound alarmist, but what is being discussed increasingly is the potential for surprises and nonlinear events. Things are changing faster than we thought."