Looking Back on the 2006 Hurricane Season

The 2006 Atlantic hurricane season officially ended on November 30th, and thankfully, there weren’t nearly as many destructive storms in 2006 as in 2005. No Atlantic storms made landfall in 2006 with hurricane strength on the Saffir-Simpson scale. Only 2 storms made landfall at all. By comparison, 8 storms made landfall at category 1 or higher in 2005, and 3 of those (including Katrina and Rita) were at least category 3.

But 2006 was not so quiet elsewhere. The National Climatic Data Center tracks 7 storm basins worldwide. So far in 2006, there have been 42 hurricanes and typhoons globally, not much below 49 in 2005. 25 of the storms in 2006 made landfall, over half of them in the North Pacific storm basin. China and the Philippines suffered the brunt of the storms in 2006. Typhoon Saomai made landfall in China as a category 4. Xangsane, Cimaron, and Durian hit the Philippines as category 4s and 5s within a 2-month time span.

What’s going on? Are hurricanes and global warming related? There are several in-depth discussions of the links between hurricanes and global warming, and contrary to popular belief, there is no short answer. Most scientists do not believe that global warming is increasing the total number of major storms (category 1-5). But there is evidence that the number of those storms that are severe (category 4 or 5) has been increasing throughout the world. The increase is correlated with a global rise in sea surface temperatures (SSTs), which is a major contributing factor to hurricane intensity. (Cyclical storm patterns, such as the so-called Atlantic Multidecadal Oscillation, explain some, but not all, of the apparent recent increases in hurricane strength.)

Source: Science Magazine, Sep 16, 2005

Most scientists believe that the question of whether global warming directly causes more intense storms or a particular storm is simply the wrong question. The better approach is that global warming impacts, especially warmer SSTs, “load the dice” for stronger storms. So global warming cannot cause stronger storms and certainly cannot cause any particular storm, such as Katrina. But global warming increases the probability that stronger storms will occur, especially over longer time spans, years or decades.

Long Term Costs of Severe Storms

In September 2005, when the United States was coming to grips with the devastation of Katrina, WRI held an internal conversation about how increasing hurricane intensity might affect how we talk about the effects of global warming. Certainly, we must be careful to not make a direct causal link between global warming and stronger storms. But we should talk about the implications of stronger storms over time:

• Vulnerability. Stronger storms will certainly cause significantly greater damage and losses, both human and economic. Typhoon Durian killed an estimated 1,000 people in the Philippines. In the United States, hurricane Katrina killed at least 1,300 people and caused an estimated $125 billion in damage. Losses are exacerbated by migration patterns; in the United States, 53% of the population lived in coastal areas in 2003, up from 48% in 1990.
• Risk. Insurance firms are already adjusting policies on what to insure, accounting for the long-term increased risks of climate change and more intense storms. The change is already causing big shocks in the housing and commercial property markets. St. Paul Travelers, the biggest commercial insurer in Louisiana, is cancelling all commercial property policies next year. Allstate Insurance has announced it will issue no more homeowners policies in Connecticut, New York or New Jersey, citing increased hurricane risk (Allstate already stopped selling new policies in Florida, Louisiana and coastal Texas).
• Strain on State and Federal Budgets. The U.S. government has authorized over $100 billion in hurricane relief for Katrina, not counting losses in the federal flood insurance program. If federal and state hurricane relief increases along with storm severity, it will increasingly compete with other spending priorities, such as defense, health care, and education. Reduced spending in these areas would have ripple effects throughout the economy.