Economic and insured losses from natural disasters have increased over recent decades, but a new report studying analyses of these events concludes anthropogenic climate change is not a main driver behind the increase.
The report, "Have Disaster Losses Increased Due to Anthropogenic Climate Change?" explains, "The observed loss increase is caused primarily by increasing exposure and value of capital at risk."
The report--to be published by the American Meteorological Society, and conducted by Laurens M. Bouwer, from the Institute for Environmental Studies at Vrije University, Amsterdam, The Netherlands--analyzed 22 peer-reviewed disaster loss studies from the last 30 years, conducted by a variety of sources that included the United Nations, the Intergovernmental Panel on Climate Change (IPCC) and some insurers. The studies analyzed mostly looked into losses in developed countries, in particular the U.S.
The studies indicated that losses from weather-related natural hazards such as storms, tropical cyclones, floods, wildfires and hailstorms have increased around the globe.
But when the studies recalculated figures, correcting for increases in population and capital at risk--called "normalization"--most of the 22 showed that disaster losses have remained constant over the time period. Eight studies did show increases after normalization, but the report states these studies did not fully correct for wealth and population increases, or other sources of exposure increases or vulnerability changes were identified.
"No study identified changes in extreme weather due to anthropogenic climate change as the main driver for any remaining trend," according to the report. It adds, "Therefore, it can be concluded that anthropogenic climate change so far has not had a significant impact on losses from natural disasters."
However, "considerable uncertainties" remain in some of the analyzed studies, the report says. Changing exposures and vulnerabilities that influence risk "can only be roughly accounted for over time," according to the study, and the potential effects of past risk reduction efforts are often ignored as data on the effects of such efforts is not available.
The report notes a clear need for analyses on the causes of increasing impacts from weather extremes, as decision-makers express concerns regarding "the consequences for insurance systems for companies and households," and as governments and companies plan for more frequent disasters and attempt to reduce exposure and risks.
Furthermore, the report notes the need for a better understanding of the relationship between anthropogenic climate change and disaster losses to inform decisions on global climate mitigation policies negotiated and developed under the United Nations Framework Convention on Climate Change.
"Studies that project future losses may give a better indication of the potential impact of climate change on disaster losses and needs for adaptation than the analysis of historical losses," the report states.
In a New York Times "Dot Earth" blog post, Andrew Revkin notes that the report's author, Ms. Bouwer, was a lead author of a chapter in the 2001 assessment from the IPCC.
