Are Hurricanes Getting Worse - or Are Humans Building In Places They Should Not?

As this is being written Hurricane Irene is visiting the New York area.

Like many tourists, she will not stay long, but her imprint on the local psyche may be more enduring than her physical impact.

Category 1 hurricanes are not usually very destructive. There may be some storm surge damage in low-lying areas, but one suspects that by next weekend the local media will be focusing on the autumn fashion, theater and film seasons.

What is noteworthy is not so much that a large-ish hurricane managed to make it to NY at all, a relatively rare event. Rather, it has thrown into high relief the nation's enduring love affair with real estate and the debate about what it means for future development. A majority of scientists believe that human-enabled climate change is creating more frequent and intense storms. There are others who disagree.

From a business perspective, however, the impact on real estate costs and insurance premiums may be more significant. People are simply building more structures in more locations because, to be frank, the best ones are gone. That is why in New York, apartments and offices are being built closer to the edges of Manhattan - east, west, south and north. Yes, some of the views are handsome, but the distance from public transportation and the daily inconvenience may well cancel the cost advantages. And as some have learned to their amazement this weekend, there may be safety issues to which the relative invincibility of affluent urban living had previously blinded them. We just hate it when reality intrudes but maybe it is a useful reminder of the limits from which many in this society are too often shielded. JL

Justin Gillis reports in the New York Times:

The scale of Hurricane Irene, which could cause more extensive damage along the Eastern Seaboard than any storm in decades, is reviving an old question: are hurricanes getting worse because of human-induced climate change?

The short answer from scientists is that they are still trying to figure it out. But many of them do believe that hurricanes will get more intense as the planet warms, and they see large hurricanes like Irene as a harbinger.
While the number of the most intense storms has clearly been rising since the 1970s, researchers have come to differing conclusions about whether that increase can be attributed to human activities.

“On a longer time scale, I think — but not all of my colleagues agree — that the evidence for a connection between Atlantic hurricanes and global climate change is fairly compelling,” said Kerry Emanuel, an expert on the issue at the Massachusetts Institute of Technology.

Among those who disagree is Thomas R. Knutson, a federal researcher at the government’s Geophysical Fluid Dynamics Laboratory in Princeton, N.J. The rising trend of recent decades occurred over too short a period to be sure it was not a consequence of natural variability, he said, and statistics from earlier years are not reliable enough to draw firm conclusions about any long-term trend in hurricane intensities.

“Everyone sort of agrees on this short-term trend, but then the agreement starts to break down when you go back longer-term,” Mr. Knutson said. He argues, essentially, that Dr. Emanuel’s conclusion is premature, though he adds that evidence for a human impact on hurricanes could eventually be established.

While scientists from both camps tend to think hurricanes are likely to intensify, they do not have great confidence in their ability to project the magnitude of that increase.

One climate-change projection, prepared by Mr. Knutson’s group, is that the annual number of the most intense storms will double over the course of the 21st century. But what proportion of those would actually hit land is another murky issue. Scientists say climate change could alter steering currents or other traits of the atmosphere that influence hurricane behavior.

Storms are one of nature’s ways of moving heat around, and high temperatures at the ocean surface tend to feed hurricanes and make them stronger. That appears to be a prime factor in explaining the power of Hurricane Irene, since temperatures in the Atlantic are well above their long-term average for this time of year.

The ocean has been getting warmer for decades, and most climate scientists say it is because greenhouse gases are trapping extra heat. Rising sea-surface temperatures are factored into both Mr. Knutson’s and Dr. Emanuel’s analyses, but they disagree on the effect that warming in remote areas of the tropics will have on Atlantic hurricanes.

Air temperatures are also rising because of greenhouse gases, scientists say. That causes land ice to melt, one of several factors leading to a rise in sea level. That increase, in turn, is making coastlines more vulnerable to damage from the storm surges that can accompany powerful hurricanes.

Overall damage from hurricanes has skyrocketed in recent decades, but most experts agree that is mainly due to excessive development along vulnerable coastlines.

In a statement five years ago, Dr. Emanuel, Mr. Knutson and eight colleagues called this “the main hurricane problem facing the United States,” and they pleaded for a reassessment of policies that subsidize coastal development — a reassessment that has not happened.

“We are optimistic that continued research will eventually resolve much of the current controversy over the effect of climate change on hurricanes,” they wrote at the time. “But the more urgent problem of our lemming-like march to the sea requires immediate and sustained attention.”