Impacts and policy responses

Hurricane-induced economic losses have increased steadily in the US over the past 50 years, with estimated total losses averaging US$35.8 billion per year during the last five years (see, for example, Pielke et al, 2005). The 2005 season was exceptionally destructive, with damages from Hurricane Katrina exceeding US$100 billion. During 2004 and 2005, nearly 2000 deaths were attributed to land-falling hurricanes in the US. Presently, 50 per cent of the US population lives within 50 miles of a coastline and the physical infrastructure along the Gulf and Atlantic coasts represents an investment of over US$3 trillion; over the next several decades this investment is expected to double. The combination of coastal demographics with the increased hurricane activity is therefore very likely to continue to escalate the socio-economic impact of hurricanes.

The risk of elevated hurricane activity arguably represents the most devastating near-term impact of global warming, particularly for the US, Caribbean and Central American regions that are impacted by North Atlantic hurricanes. How should policy makers and other decision makers react to the risk of elevated hurricane activity associated with global warming in the face of the scientific uncertainties?

To address the short-term (decadal) impacts of elevated hurricane activity, decreasing our vulnerability to damage from hurricanes will require a comprehensive evaluation of coastal engineering, building construction practices, insurance, land use, emergency management and disaster relief policies. Any conceivable policy for reducing CO2 emissions or sequestering CO2 is unlikely to have a noticeable impact on sea surface temperatures and hurricane characteristics over the next few decades; rather, any such mitigation strategies would only have the potential to impact the longer-term effects of global warming. On the time scale of a century, sea level rise will compound the impact of increased hurricane activity by increasing vulnerability to storm surge. By 2100, a sea level rise of 0.3—0.6 m (or even more) is plausible. Hurricane prone regions in the US at greatest risk from storm surge enhancement associated with greenhouse warming include New Orleans, South Florida and portions of the mid-Atlantic coast.

Looking globally, Bangladesh is particularly vulnerable to the combination of increased hurricane intensity and sea level rise; several hundred million people live in the southern part of the country where the elevation is only a few feet above sea level, and three tropical cyclones during the 20th century each killed over 100,000 people. In Central America, there is substantial vulnerability associated with landslides, and the vulnerability is exacerbated by deforestation; Hurricane

Mitch in 1998 resulted in more than 75 inches of rain and catastrophic landslides that killed more than 11,000 people. The vulnerability of the developing world to increased hurricane activity and sea level rise raises not only the obvious humanitarian and economic issues, but also the potential for regional instabilities and international security concerns that could be associated with mass migrations of refugees.

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