It's easy to use the tragedy of Hurricane Katrina to call attention to human-caused global warming, as Nicholas Kristof did in his New York Times column on Sunday. But the scientific evidence currently is too thin to blame Katrina and other hurricanes on carbon dioxide emissions. And environmentalists may risk embarrassment if they exploit the theoretical link to promote their causes.
Virtually every objective climate scientist now accepts that humans are causing the Earth to baste like a meatball on a skewer with the help of CO 2 and a whole family of gases, which have been belching from auto exhaust pipes and drifting from industrial chimneys for the last 20 decades or so. The average Earth surface temperature has gone up about one degree in the past 100 years, and scientists expect a rise of between one and four more degrees over the next 50. That may not sound like much, but in the delicately balanced climate of the Earth it's enough to produce some big changes: a dramatic shrinkage of ice around the North and South poles, the retreat of mountain glaciers, slightly warmer oceans, and a rise in the global sea level of 4 to 8 inches.
Scientists also agree that in recent years, hurricanes have become more frequent and severe, at least in the Atlantic Ocean. After 24 years of relative quiet, more than 30 major hurricanes have churned in the Atlantic since 1995. Most researchers, however, think that increase has nothing to do with global warming. Those who study tropical cyclones say that Katrina was part of a natural cycle of angry storms that will batter North America for decades. "These changes in hurricane activity are viewed as resulting from long-period natural climate alterations that historical and paleo-climate records show to have occurred many times in the past," Philip Klotzbach and William Gray of the hurricane-forecast team at Colorado State University, which has been forecasting hurricane season activity since 1984, say in a statement released by the university in August.
There is one hurricane scientist who believes he has found a possible link between global warming and storm intensity. But it's an entirely theoretical one. In the Aug. 4 edition of Nature, Kerry Emanuel of the Massachusetts Institute of Technology presented math models that he said "show a substantial increase in potential intensity with anthropogenic global warming, leading to the prediction that actual storm intensity should increase with time." Emanuel concedes, however, that the observed storm intensities do not match what the models predict and that his study can only "suggest" that global warming "may" lead to more intense storms. In the New York Times last week, he agreed with Gray and Klotzbach that the increase in hurricane activity the last two years "is mostly the natural swing."
Until the science clarifies, environmental groups that use Katrina as a way to boost their campaign for tougher controls on greenhouse emissions risk provoking a backlash. Exploiting bad news and facile pseudoscience to seek support and fresh donations is a good way to lose credibility. Greenpeace, for instance, looked foolish when it denounced genetically modified foods as "Frankenfoods" that can potentially harm human health. The Institute of Medicine of the National Academy of Sciences, a respected independent advisory group, concluded in 2004 that foods created by gene manipulation were no more dangerous than crops altered by traditional breeding methods. The animal-rights movement suffered a similar embarrassment when it argued against using laboratory animals for medical research by claiming that computer modeling could accomplish the same research goals as living animals. Donald Kennedy, executive editor in chief of the journal Science, called the claim "a remarkable piece of science fiction."
Environmentalists who want to leverage Katrina are on far more solid ground scientifically and economically in going after the state and federal rules that permit people to build in harm's way. Population growth along the U.S. coastline has exploded in recent years—13 million people now live in Florida's coastal counties alone compared to only about 200,000 a century ago. A USA Today study concluded that about 1,000 people move into U.S. coastal counties each day. The denser population makes the areas more difficult to evacuate: Officials told the Washington Post that it now takes twice as long to evacuate Biloxi and Gulfport, Miss., as it did 10 years ago.
All this is sure to increase the death toll in a major storm. Yet that risk is blithely ignored in many coastal developments, often with the support of elected officials. For instance, when an Army deputy assistant secretary tried to block applications to build a casino along a fragile marsh area in Mississippi in 1998, Republican Sen. Trent Lott of Mississippi persuaded the Army to issue the permits; Lott had earlier attended a $100,000 casino-industry fund-raiser for the GOP. Now 20 of those Mississippi casinos have been smashed by Katrina.
The historic pattern has been that as soon as crises pass, more buildings go up and new people move in. As John Tierney, among others, pointed out last week, property owners don't have much financial incentive to respect the risks of living in a hurricane zone. The federal government's flood insurance stakes property owners to much of the cost of rebuilding on the site that's been inundated. Studies show that thousands of coastal dwellers have received federal insurance payments for the same site following at least two different floods. In rare instances, homes have been restored many more times than those with federally backed insurance: A Canton, Miss., property, currently worth about $49,300, has had 25 losses in 18 years at a restoration cost of $181,279.
The Flood Insurance Reform Act, signed into law by President George W. Bush in June 2004, could change some of this. The new law is designed to discourage property owners from rebuilding in repeatedly flooded areas and would help homeowners to either elevate their homes or to build on high and dry sites. But the law on its own isn't enough. The president did not include funding for the Flood Insurance Reform Act in his 2005 or 2006 budgets. And given the powerful sentiment to rebuild New Orleans on its below-sea-level site, and the promise of Mississippi officials to restore that state's coastal area to its pre-storm glory, the historic pattern of rebuilding in flood zones is likely to be repeated. As estimates for the total recovery costs of Katrina edge toward $200 billion, environmentalists should ask what that money is getting us.