Increasing hurricane damages

A conference called the Hurricane Science for Safety Leadership Forum convened this week in Orlando to look at how we can better prepare for the inevitable hurricanes in our future. The conference brought together an interesting mix of experts--scientists from environmental groups like the National Wildlife Federation, insurance industry representitives, and a representative from the pro-business Competitive Enterprise Institute (CEI).

There are a number of interesting Powerpoint and video presentations posted on their web site, for those interested. The most eye-opening fact I saw came during a presentation done by Amanda Staudt of the National Wildlife Federation. In her presentation on the policy implication of hurricanes and climate change, she showed that the population of South Florida is projected to grow from a 1990 population of 6.3 million to a 2050 population of 15-30 million people. That's a startling increase in population. Higher and higher hurricane damage tabs are inevitable in coming decades, just from this huge increase in population. She goes further, showing that if the theoretical predictions for global warming by the end of the century come true--a 2-13% increase in hurricane winds due to ocean warming, a 10-31% increase in hurricane rainfall, and an increase in sea level of several feet--there is likely to be a huge increase in hurricane damage, and probably in deaths, as well.

I have a few comments on this. While I believe that hurricane damages will continue to grow primarily because of population increases, higher wealth, and poor land management, the contribution of increased damage due to global warming will start to become significant by the end of the century. The 5% increase in hurricane winds per °C of ocean warming theorized by hurricane researcher Dr. Kerry Emanuel (Emanuel, 2005) may not seem like much, it will make a significant difference in the destructive power of the strongest storms. A Category 4 hurricane does about four times more damage than a Category 3 hurricane, and 250 times more damage than a Category 1 storm (Figure 1). Given the expected increase of tropical sea surface temperatures of 1-2 °C by 2100, hurricane wind speeds should increase by 5-10%. Since the difference in wind speed between a Category 3 and Category 4 hurricane is about 15%, we can anticipate that the strongest hurricanes in 2100 will do 1 1/2 to 3 times more damage than they do now.

This may be an underestimate of the increase in damage, though. Global sea level rose about 0.75 feet last century, and is expected to rise 0.6 - 1.9 feet this century, according to the "official" word on climate, the 2007 report of the U.N.'s Intergovernmental Panel on Climate Change (IPCC). A paper published by Pfeffer et al. in Science this year concluded that the IPCC underestimated sea level rise, and that the "most likely" range of sea level rise by 2100 is 2.6 - 6.6 feet. If true, we can expect greatly increased damage from hurricane storm surges. However, it is possible that there will be fewer hurricanes by the end of the century, thanks to an increase in wind shear over the tropical Atlantic (Vecchi and Soden, 2007).


Figure 1. Potential hurricane damage as a function of Saffir-Simpson category for U.S. hurricanes between 1925-1995. If the median damage from a Category 1 hurricane is normalized to be a "one", then Category 2, 3, and 4 hurricanes were 10, 50, and 250 times more damaging, respectively. Data taken from Pielke, Jr. R. A., and C. W. Landsea, 1998: "Normalized Atlantic hurricane damage 1925-1995" Wea. Forecasting, 13, pp.621-631.

Better building codes
Congressman Bennie Thompson, D-MS, Chairman of the House Homeland Security Committee, helped to kick off the conference with opening remarks that underscored his intention to hold Congressional hearings on developing new building codes in hurricane-prone areas. He was hopeful that President-elect Obama and new incoming head of Homeland Security, Arizona Gov. Janet Napolitano, would work to adopt new, tougher building standards. "Take a look at the homes on the Bolivar Peninsula in Texas that are still standing after the hurricane," Thompson said. "We know how to build stronger homes. Now we just need to do it." Thompson said that while such legislation had been introduced in the past but failed, chances were better under an Obama administration of passage.

I think it is essential that more stringent and comprehensive building codes get adopted in hurricane alley to reduce the inevitable huge price tags from future hurricanes.

References
Emanuel, K. 2005, "Increasing destructiveness of tropical cyclones over the past 30 years", Nature, 436, 4 August 2005, doi:10.1038/nature03906.

Vecchi, G.A., and B.J. Soden, 2007, "Increased tropical Atlantic wind shear in model projections of global warming", Geophys. Res. Lett., 34, L08702, doi:10.1029/2006GL028905, 2007.

Jeff Masters