Did global warming cause Sandy?
Experts are saying Hurricane Sandy is one for the record books, considering not only the storm’s size but unique track. So why are we experiencing a storm like no other? With reports like the one Environment Rhode Island released earlier this year blaming global warming for a predicted 90 percent increase in severe storms, it’s not surprising that some have pointed to the Earth’s climbing temperature as a cause for mammoth storms like Sandy.
But some, like Atmospheric Scientist Angela Fritz from Weather Underground, an online weather service, said whether or not Sandy would have developed without global warming is “debatable.”
“There are some things we know for sure,” said Fritz yesterday in an email. “A warmer atmosphere means there's more moisture in it, which means more rain.”
The increase in moisture means more severe floods and rising sea levels. With rising seas come greater storm surges, which in turn affect coastlines.
“Storm surges will continue to have a larger and larger impact on coastlines, especially coastlines where tropical cyclones are not common and the communities might not be prepared,” she said.
The kicker with Sandy, though, is the unusual left hook she’s taken toward the East Coast of the U.S., a pattern that has never been documented before according to Bob Henson, a writer for the National Center for Atmospheric Research and author of “The Rough Guide to Climate Change.” Henson said the strange pattern will account for an increased storm surge, especially for communities like Long Island, since the wind will be blowing from the east, versus the south.
So why is Sandy behaving so strangely? Henson and Fritz agree it’s because of a block of high pressure (or as Henson said in layman’s terms, “a blob of warm air”) up near Greenland. This “blob,” said Henson, is warmer than usual and has lasted longer than typically observed. Fritz said global warming might be a factor in this particular aspect of the storm.
“The large-scale weather pattern we're seeing right now, which is causing Sandy to take a beeline into the East Coast … has been shown to be more likely in a global warming scenario,” she said.
In addition to maintaining high-pressure systems like the one in Greenland, global warming also means warmer water temperatures, a key in sustaining tropical storms like Sandy. This year boasts the warmest fall water temperatures on record, which helped keep Sandy going as it traveled up the Atlantic.
Henson noted that the Atlantic Ocean has been going through a “warm phase” that started in the mid-1990s, which was when extreme storms started to make an appearance. These warm water phases typically last 20 to 30 years, he said.
Henson said it is too soon to say if Sandy’s severity was directly caused by climate change, though he has no doubt there will be extensive studies done on the storm to determine just that. But weather, he said, is not caused by climate change; instead, weather has “a little climate change in the background,” which causes variations.
Overall, because of the interaction between Hurricane Sandy, the high-pressure system in the north and the jet stream, this massive weather event is what Henson is calling “extremely rare.”
Rare and massive, too – Henson said Sandy has the largest wind field on record, and Fritz said it beats out the radius of 1988’s Olga by 25 miles.
“This is an incredibly huge storm with tropical-storm force winds extending more than 500 miles from the center of circulation,” said Fritz. “This means these winds are covering the driving distance from Boston to Charlotte [North Carolina.]”
Henson said he expects hurricanes in the future to increase in intensity, but become less frequent, a prediction that mirrors general precipitation trends. Fritz said the increase in global temperatures will bring a subsequent increase in extreme weather events.
“This has been shown in numerous scientific studies,” she said. “The impacts are most directly related to heat, drought and wildfires, but it's also related to not-so-obvious things like rain, flooding, snowfall, and in this case, hurricanes. I think we're in a situation where we're seeing ‘crazy weather’ more and more, and I suspect this trend will continue as we continue to modify our atmosphere and our environment.”
Despite the huge size and record-breaking trajectory, Sandy was not a terribly strong storm, ranking only in the lowest wind category of Hurricanes. Sandy is the 10th tropical cyclone to reach Hurricane status (sustained winds of at least 74 mph) this season.