So-called 'storms of the century' like last August's Hurricane Irene could become almost commonplace, thanks to climate change.
A team from MIT and Princeton University says that such storms could make landfall far more frequently, causing powerful, devastating storm surges every three to 20 years.
The group simulated tens of thousands of storms under different climate conditions, and concluded that the sort of severe floods which now hit every five hundred years or so could, with climate change, start happening once every 25 to 240 years.
MIT postdoc Ning Lin says that planners should take the findings into account when designing seawalls and other protective structures.
“When you design your buildings or dams or structures on the coast, you have to know how high your seawall has to be,” Lin says. “You have to decide whether to build a seawall to prevent being flooded every 20 years.”
To simulate present and future storm activity, using New York City as a case study, the researchers combined four climate models with a specific hurricane model. The combined models generated 45,000 synthetic storms within a 200-kilometer radius of Battery Park, at the southern tip of Manhattan.
They studied each climate model under two scenarios: a 'current climate' condition representing 1981 to 2000 and a 'future climate' condition for 2081 to 2100, based on the Intergovernmental Panel on Climate Change’s projections of future moderate carbon dioxide output. While there was some variation among the models, most showed that more intense storms would be caused by climate change.
The team also modeled the effects of storm surges, using models including the one used by the National Hurricane Center (NHC).
Today, a surge flood of about two meters hits New York about every 100 years, with three-meter surge floods coming about every 500. Manhattan’s seawalls aren't actually designed for either, standing just 1.5 meters high.
And with added greenhouse gas emissions, says the team, a two-meter surge flood would occur once every three to 20 years; a three-meter flood every 25 to 240 years.
"The physical damage and economic loss that result from storm surge can be devastating to individuals, businesses, infrastructure and communities," says Carol Friedland, an assistant professor of construction management and industrial engineering at Louisiana State University.
"For current coastal community planning and design projects, it is essential that the effects of climate change be included in storm-surge predictions."