The Storm Next Time


New York Times

September 11, 2005

If the White House wants to move the debate about Hurricane Katrina beyond what it calls the "blame game" for bodies decomposing in the streets of New Orleans, then here's a constructive step that President Bush could take to protect people in the future: Tackle global warming.

True, we don't know whether Katrina was linked to global warming. But there are indications that global warming will produce more Category 5 hurricanes. Now that we've all seen what a Katrina can do - and Katrina was only Category 4 when it hit Louisiana - it would be crazy for President Bush to continue to refuse to develop a national policy on greenhouse gases.

"The available scientific evidence indicates that it is likely that global warming will make - and possibly already is making - those hurricanes that form more destructive than they otherwise would have been," declares an analysis by five climate scientists at

Hurricanes derive their power in part from warm water, and so forecasting models show future hurricanes becoming more severe as sea surface temperatures rise. One summary of 1,200 simulations published in the Journal of Climate last year showed that rising levels of greenhouse gases could triple the number of Category 5 hurricanes. (A link to this study and others appear below this column.)

Moreover, there's empirical evidence that hurricanes have already become more intense (but not more frequent). Nature magazine this summer reported a new study by Kerry Emanuel, a hurricane guru at M.I.T., indicating that by one measure hurricanes have almost doubled in intensity over the last 30 years.

That reflects natural cycles as well. But Professor Emanuel writes: "The large upswing in the last decade is unprecedented, and probably reflects the effect of global warming."

He adds: "My results suggest that future warming may lead to ... a substantial increase in hurricane-related losses in the 21st century."

Global warming also makes hurricanes more destructive by raising the sea level. One Environmental Protection Agency study foresees a one-foot rise in sea levels on the Atlantic and Gulf coasts by 2050 and a two-foot (and possibly four-foot) rise by 2100.

A two-foot rise would swallow a chunk of the United States bigger than Massachusetts, according to the E.P.A., and would also result in much more coastal flooding. One study by FEMA found that just a one-foot rise in sea levels would increase flood damage by 36 to 58 percent - underscoring that we need to bolster coastal protections as well as curb carbon emissions.

So far, Mr. Bush has resisted serious action on global warming on the basis that strong measures "would have wrecked our economy."

Tell that to Portland, Ore. In early July, I wrote a column from Portland about its pioneering efforts to cut greenhouse gases. New calculations had indicated that it had cut total emissions below the level of 1990 - the benchmark for the Kyoto accord - even as nationally, emissions have increased 13 percent. And Portland has been booming economically.

Since then, Portland has discovered a small error in its calculations: In fact, total emissions were reduced to a hair over 1990 levels, not to a hair under. In any case, while the numbers aren't perfect, the trend is clear.

So Portland remains a model for what the Bush administration could do if it wanted to get serious about climate change. The steps Portland took included encouraging walking and bicycle commuting, telling local companies that if they give employees free parking they should also subsidize bus passes, and replacing bulbs in traffic lights with light-emitting diodes that cut electrical use by 80 percent. That last move saved the city almost $500,000 a year in electrical costs. I can't figure out why Mr. Bush is so reluctant to embrace such steps.

Portland has also put teeth into its environmentalism by joining the Chicago Climate Exchange and making a legally binding commitment to reduce emissions. The Chicago Climate Exchange also counts as members cities like Chicago and Oakland, as well as universities like Tufts and the University of Minnesota. Those members are leading the way in addressing climate change - a contrast with the paralysis in Washington.

With corpses on the streets of New Orleans, we may have seen a glimpse of the future of climate change. Let's hope it shakes Mr. Bush out of his complacency.

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A starting place to learn about the linkage between hurricane intensity and global warming is The essay at the top of that page is very useful, as is the thread of discussion among meteorologists below it. There is also some discussion there of another essay to be published in the Bulletin of the American Meteorological Society, available for viewing here: That essay is more skeptical, agreeing that global warming will make hurricanes more severe but suggesting that the impact will be more modest, perhaps adding only 1 to 10 miles per hour to a hurricane's wind speed.

In contrast, see Kerry Emanuel's "Increasing Destructiveness of Tropical Cyclones Over the Past 30 Years," Nature magazine, 4 August 2005: The Journal of Climate article I mention, about simulations suggesting that warming temperatures lead to more Category 5 hurricanes, is here: See especially figure 6.

Note that there are various charts of hurricanes striking the U.S., pointedly showing no increase in the number lately. That proves nothing, since nobody argues that global warming increases the frequency of hurricanes, only the intensity. And in any case, since relatively few serious hurricanes actually strike the U.S., it's hard to draw conclusions from annual fluctuations.

For more information on Portland's efforts to reduce greenhouse gas emissions, see

The Chicago Climate Exchange is an excellent idea, and more info is here: