Post image for Global Warming Has No Significant Impact on Disaster Losses, Study Finds

Global Warming Has No Significant Impact on Disaster Losses, Study Finds

by Marlo Lewis on June 1, 2011

in Features

Al Gore’s film An Inconvenient Truth bombarded audiences with image after image of hurricanes, tornadoes, floods, forest fires, and drought, creating the impression of a world in climate chaos. Gore blamed the alleged upsurge in extreme weather on global warming, that is, mankind’s sins of emission. One of Gore’s mighty pieces of evidence was a dramatic increase in insurance payments for weather-related damages. As he writes in his best-selling book of the same title:

Over the last three decades, insurance companies have seen a 15-fold increase in the amount of money paid to victims of extreme weather. Hurricanes, floods, drought, tornadoes, wildfires and other natural disasters have caused these losses [An Inconvenient Truth, p. 101].

Gore presented a chart similar to this one:

Seeing is believing, right? The problem, of course, is not merely that correlation (warmer weather/bigger losses) does not prove causation. More importantly, the economic data depicted in the chart have not been adjusted (“normalized”) to offset increases in population, wealth, and the consumer price index.

Consider this fact: More people today live in just two Florida counties, Dade and Broward, than lived in all 109 coastal counties from Texas to Virginia in 1930. Florida’s population grew by more than 17.5% in the past decade alone and today is 48% larger than in 1980. There’s tons more stuff in harm’s way than there used to be. No wonder damages are bigger than in the good old days!

Most studies that “normalize” economic loss data find no evidence of a trend towards more violent or destructive weather. Here, for example, is a chart from a study on normalized hurricane damages by Pielke, Jr et al. 2008:

Figure description: U.S. hurricane damages, 1900-2005, if all hurricane strikes had hit the same locations but with year 2005 population, wealth, and consumer price index.

A study published earlier this year in the Bulletin of the American Meteorological Society (Bouwer, L.M. 2011. Have disaster losses increased due to anthropogenic climate change?) examines 22 previous studies on the oft-asserted link between climate change and weather-related damages.

Here’s what the researcher, Laurens M. Bouwer of the Institute for Environmental Studies in the Netherlands, found:

All 22 studies show that increases in exposure and wealth are by far the most important drivers for growing disaster losses. Most studies show that disaster losses have remained constant after normalization, including losses from earthquakes (see Vranes and Pielke 2009). Studies that did find increases after normalization did not fully correct for wealth and population increases, or they identified other sources of exposure increases or vulnerability changes or changing environmental conditions. No study identified changes in extreme weather due to anthropogenic climate change as the main driver for any remaining trend.

Bouwer concludes:

The studies show no trends in losses, corrected for changes (increases) in population and capital at risk, that could be attributed to anthropogenic climate change. Therefore, it can be concluded that anthropogenic climate change so far has not had a significant impact on losses from natural disasters.

CO2Science.Org has an excellent review of the Bouwer study. On a related issue, World Climate Report reviews a recent study finding no long-term increase in the number of Atlantic tropical storms and hurricanes over the past 130 years. The apparent increase in storm frequency turns out to be an artifact of the data, that is, a product of the increase in spatial coverage and accuracy of hurricane monitoring systems.

Previous post:

Next post: