When the words "hurricane" and "global warming" end up in the same sentence in a news story, typically the subject is whether climate change is or will make Atlantic hurricanes stronger or more frequent. Unlike many other aspects of climate change, that's one point where legitimate scientists argue, and the jury is still out. But when it comes to the damage that hurricanes are likely to do when they make landfall in the U.S., there's considerably less debate.
For one, more people live along the coasts than ever, and people continue to move there despite the ongoing seasonal risk of tropical storms and hurricanes. As of 2003, more than half of the U.S. population lived along the coast, and the 153 million people living there at that time had grown nearly 30% in 25 years, according to a 2008 National Oceanographic and Atmospheric Administration study. Since 2003, the U.S. experienced the real estate bubble and a building boom, adding substantially to the homes in hurricane risk zones.
Along the East Coast, where Hurricane Irene's path is expected to track, population has increased dramatically, as people purchased homes, or vacation homes, along the coast.
And one aspect of all hurricanes is becoming more dangerous: Storm surge. Why? Sea-level rise.
Storm surge is water pushed toward the shore by storm winds. The higher sea levels are to start, the greater the risk from storm surge. Unappreciated by many people, it's storm surge not rain, not wind that kills most people during hurricanes.
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Sea levels were stable for about 2,000 years, but have been rising worldwide for the last century, most likely due to climate change, according to international and U.S. scientific estimates. Global warming fills oceans with melting ice and swells the water itself, as it warms. Along the U.S. East Coast, where Hurricane Irene is headed, sea levels rose about six inches more than the global average in the last century, a total of about a foot overall. In New Jersey, for instance, sea level is rising about an inch every six years.
Just looking back to past hurricanes that have hit the Northeast, historic storms came in 1938, 1944, 1954 and 1960, when sea levels were roughly a half foot lower than they are today.
Over the next century, global sea levels are predicted to rise between 7 inches and nearly two feet. (In prehistoric global warm periods, sea level was as much as 20 feet higher than today.)
For every one-foot rise in sea level, U.S. scientists estimate a 36-58% increase in damage from storm surge. For a three-foot rise, the damage doubles or tripling of damages.
A few inches or a foot might not seem like much, but when that foot means the difference between the surf and your home, or your water treatment plant, it makes all the difference. The latest forecast from the National Hurricane Center for Hurricane Irene includes this warning:
STORM SURGE...AN EXTREMELY DANGEROUS STORM SURGE WILL RAISE WATER LEVELS BY AS MUCH AS 6 TO 11 FEET ABOVE GROUND LEVEL IN THE HURRICANE WARNING AREA IN NORTH CAROLINA...INCLUDING THE ALBEMARLE AND PAMLICO SOUNDS. STORM SURGE WILL RAISE WATER LEVELS BY AS MUCH AS 4 TO 8 FEET ABOVE GROUND LEVEL OVER SOUTHERN POTIONS OF THE CHESAPEAKE BAY...INCLUDING TRIBUTARIES...AND THE EASTERN SHORE OF THE DELMARVA PENINSULA. STORM SURGE WILL RAISE WATER LEVELS BY AS MUCH AS 3 TO 6 FEET ABOVE GROUND LEVEL ALONG THE JERSEY SHORE. NEAR THE COAST...THE SURGE WILL BE ACCOMPANIED BY LARGE... DESTRUCTIVE...AND LIFE-THREATENING WAVES.
See how storm surge could affect where you live, with NOAA's Hurricane Irene storm surge map.
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