Friday, September 19, 2008

A Warming World: More Hurricanes Like Ike?

In the wake of Hurricane Ike’s devastating hit on Galveston and the Gulf Coast, discussion swirls around the role of global warming in creating both more and larger hurricanes.

As I noted today on WHYY’s “Morning Edition,” you can’t pin any one hurricane on global warming. But you can look for long-term trends.

So the
Pew Center for Climate Change has discovered that between 1850 and 1990, there were, on average, 10 tropical storms in the North Atlantic annually, five of which became hurricanes.

Since 1995, the average number has jumped to 14, eight of which were hurricanes. The North Atlantic shows an increase in hurricane activity in the last decade, a possible fingerprint for global warming.

But don’t get cocky: oddly enough, there is no evidence for more hurricanes worldwide. So scientists continue to wring their hands over evidence.

Still, the UN’s
Intergovernmental Panel on Climate Change, the group that won the Nobel Peace Prize alongside Al Gore, weighed in last year: the probability that GW makes more hurricanes “is more likely than not.” A tepid but appropriate response as science continues to weigh the evidence.

Meanwhile, the
National Wildlife Federation has just released a study that says that when hurricanes do form, global warming gives them a three-fold wallop:

Hurricanes will be stronger with more winds.

They will bring heavier rainfall.

And they will cause more flooding because of a larger storm surge.

Their data says a warmed atmosphere over a warmed ocean—the fuel that powers hurricanes—will push wind speeds up some 13%, nudging some storms from dangerous Category 3 to catastrophic Katrina-level Category 4.

Rainfall can increase between 10 and 31% over normal; Hurricane Fay, the one that managed to hit Florida four times, a record, dropped 27 inches of rain in some places. 27 inches: almost what Philadelphia gets in a full year!

And Ike traveled north after Galveston, dropping nine inches of rain in Chicago a couple of days later, causing horrific flooding up there.

And if powerful winds push storm surges higher, there will be more flood damage. Since 1998, some dozen hurricanes have topped $1 billion in damage, capped by Katrina, raining down $125 billion in destruction. Who knows what Ike’s bill will be; the costs mount daily.

To mitigate flood damage, NW reminds us that beaches were once the barriers that protected the mainland from storms—the loss of wetlands in New Orleans exacerbated Katrina’s damage. They are sponges that absorb storm surges and excess water.

Every mile of healthy wetlands, they say, can trim 3-9 inches off a storm surge. Yet wetlands continue to vanish under an assault of development.

And one acre of wetlands reduces hurricane damage by $3,300. String together thousands of acres, and you’ve got something. In fact, Texas and Galveston have begun an intense debate on whether or not homeowners can rebuild on the barrier beaches.

Let’s first just acknowledge that in the last 20 years, there has been a building boom on beaches—a potential accident waiting to happen.

The impact of global warming on hurricanes is, of course, controversial in some circles: just check out the web site of for starters.

No matter how you feel about the issue, this is a critically important discussion, and the defining era of this, the Greenhouse Age.

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