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Insurers' disaster files suggest climate is culprit

Naturevolume 441page674 (2006) | Download Citation

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Rising costs hint at weather effect.

Munich

Insurance companies, acutely aware of the dramatic increase in losses caused by natural disasters in recent decades, have been convinced that global warming is partly to blame. Now their data seem to be persuading scientists, too. At a recent meeting of climate and insurance experts, delegates reached a cautious consensus: climate change is helping to drive the upward trend in catastrophes.

The meeting, held near Munich on 25–26 May, was jointly organized by Munich Re, the world's largest reinsurance company, and the University of Colorado in Boulder. It brought together climate, atmosphere and weather researchers with economists and insurance experts to discuss what could be behind recent disaster losses, both economic and human. Insurers have been outspoken in blaming global warming. But scientists have tended to be more cautious, with many arguing that the rise could be primarily due to socioeconomic changes and natural climate variability.

Under discussion were data compiled by Munich Re, whose NatCatservice database, comprising 22,000 natural disasters dating back to ad 79, is the largest of its kind. NatCatservice shows that the frequency of weather-related catastrophes has increased sixfold since the 1950s. The number of non-weather disasters, such as earthquakes, tsunamis and volcanic eruptions, has only marginally increased during the same period.

An ill wind: an April storm destroyed this house in Tennessee, and the weather seems set to worsen. Credit: M. BROWN/AP

Delegates seem to have found the record persuasive. Their consensus statement, to be released on 8 June, says there is “evidence that changing patterns of extreme events are drivers for recent increases in global losses”.

There was no agreement on how big a role global warming has played, however. “Because of issues related to data quality, it is still not possible to determine the portion of the increase in damages that might be attributed to climate change,” the workshop concluded.

“Dissent over the issue is clearly waning,” says Peter Höppe, head of Munich Re's Geo Risks department, who co-chaired the workshop with Roger Pielke Jr, director of the University of Colorado's Center of Science and Technology Policy Research. “Climate change may not be the dominant factor, but it has become clear that a relevant portion of damages can be attributed to global warming.”

Previously sceptical, Pielke says that he is now convinced that at least some of the increased losses can be blamed on climate: “Clearly, since 1970 climate change has shaped the disaster loss record.”

He adds a note of caution, however: “Disaster damage is not the place to look for early indications of climate change,” he says. “Policy advocates should exercise caution in using disaster losses to justify climate mitigation, lest they go beyond what science can support.”

But environmental groups are already using the rise in extreme weather events to help their campaigns about climate change. For example, Germanwatch, an environmental and developmental watchdog group, has used the Munich Re data to compile a ranking of the countries most badly affected by weather-related disasters in 2004.

The group ranked countries according to four indicators — the number of casualties from extreme weather events, the number of casualties per 100,000 population, total economic damages, and economic damages relative to the country's gross domestic product. It combined those rankings to give a final “climate risk index”. The ranking is topped by Somalia and other underdeveloped countries. But the United States and Japan, where natural disasters in 2004 caused considerable economic losses, also ranked highly.

The list has been criticized by experts, who say that data for a single year are largely influenced by random events and reveal little about how climate change is affecting different countries. But Sven Anemüller, co-author of the report and senior adviser for climate and development with Germanwatch, counters that the 2004 list is just the beginning of a longer-term analysis. “We're not saying that the countries listed this time are the ones that will lastingly be hit hardest by climate change,” he says.

The group's approach, if continued, does make sense, agrees Höppe. Looking at the rankings over years or decades could eventually provide much-needed information as to which countries are most at risk from climate change, he says.

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