Background
The author -- with Vrije Universiteit's Institute for Environmental Studies in Amsterdam, The Netherlands -- writes that "the recent global assessment report on natural disasters of the United Nations shows that the number of natural disasters, economic losses, and number of people affected are increasing at a rapid rate, faster than risk reduction can be achieved (UN-ISDR, 2009)," noting, however, that a "better understanding of the relationship between anthropogenic climate change and disaster losses is needed to inform decisions on global climate change mitigation policy."

What was done
In an attempt to obtain this "better understanding," Bouwer provides "an overview of recent quantitative studies and by assessing the role of climate change in disaster loss increases relative to other changes." More specifically, by means of a search of the peer-reviewed literature he identified 22 studies that systematically analyzed well-established records from natural hazard loses that included monetary damages and extended over a period of at least 30 years; and from the results of these studies he reached his conclusions. The specific hazards treated by the 22 studies included bushfire, earthquake, flood, hail, landslide, windstorm, thunderstorm, tornado, tropical storm, hurricane and hail, while the study regions included Australia, China, Europe, India, Korea, Latin America, Switzerland, the United States and the world as a whole.

What was learned
The Dutch researcher reports that "most of the 22 studies have not found a trend in disaster losses, after normalization for changes in population and wealth." In fact, he says that "all 22 studies show that increases in exposure and wealth are by far the most important drivers for growing disaster losses [italics added]," a conclusion that has also been reached by Changnon et al. (2000), Pielke et al. (2005) and Bouwer et al. (2007). And he adds that "no study identified changes in extreme weather due to anthropogenic climate change as the main driver for any remaining trend."

Reiterating these observations in his paper's concluding paragraph, Bouwer says that although "economic losses from various weather-related natural hazards, such as storms, tropical cyclones, floods, and small-scale weather events (e.g., wildfires and hailstorms), have increased around the globe," the 22 studies he analyzed "show no trends in losses, corrected for changes (increases) in population and capital at risk, that could be attributed to anthropogenic climate change."

What it means
In a final straightforward statement of fact, Bouwer says "it can be concluded that anthropogenic climate change so far has not had a significant impact on losses from natural disasters."

References
Bouwer, L.M., Crompton, R.P., Faust, E., Hoppe, P. and Pielke Jr., R.A. 2007. Confronting disaster losses. Science 318: 753.

Changnon, S.A., Pielke Jr., R.A., Changnon, D., Sylves, R.T. and Pulwarty, R. 2000. Human factors explain the increased losses from weather and climate extremes. Bulletin of the American Meteorological Society 81: 437-482.

Pielke Jr., R.A., Agrawala, S., Bouwer, L.M., Burton, I., Changnon, S., Glantz, M.H., Hooke, W.H., Klein, R.J.T., Kunkel, K., Mileti, D., Sarewitz, D., Thompkins, E.L., Stehr, N. and von Storch, H. 2005. Clarifying the attribution of recent disaster losses: A response to Epstein and McCarthy. Bulletin of the American Meteorological Society 86: 1481-1483.

UN-ISDR. 2009. Risk and poverty in a changing climate: Invest today for a safer tomorrow. United Nations International Strategy for Natural Disaster Reduction Global Assessment Report on Disaster Risk Reduction.