A study looking back over 1,000 years finds the flooding risk along the New York and New Jersey coasts increased greatly after industrialization, and major storms that once might have occurred every 500 years could soon happen every 25 years or so.

The study by Penn State, Rutgers, Princeton and Tufts universities and Massachusetts Institute of Technology finds that flood heights have risen nearly 4 feet since the year 850, largely because of a sea level rise. The study advocates better risk management strategies to cope with storms.

It was released a month before the third anniversary of Superstorm Sandy, which devastated the coasts of New York and New Jersey. “A storm that occurred once in seven generations is now occurring twice in a generation,” said Benjamin Horton of Rutgers, one of six lead researchers involved. “What we do know is that as sea level rise accelerates into the future, we are going to have more frequent flooding.”

The study was published in the Proceedings of the National Academy of Sciences journal.

Adam Sobel, an atmospheric scientist at Columbia University, said this study, like many others before it, leaves little doubt that sea level rise will be more rapid than it has been before. “This is just one more good study adding certainty to what we know already, which is that coastal cities around the world — including New York, but we’re not the only one, nor the worst — are in trouble,” he said. “This makes the direction of change certain: We are at increasing risk for Sandy-like disasters here in New York City and in many other places as well.”

Global sea level has already risen about a foot since 1900, and is projected to rise as much as 39 inches by the end of the century. Hurricanes are also expected to be stronger and more frequent. “We found that the biggest tropical cyclones tend to be larger, with a larger radius and maximum winds of these storms in the later anthropogenic time period,” Reed said. “We also found that the most intense storms are even more intense in the later time period.”

“The study is the preamble for what we have to be concerned about,” said Klaus Jacob, special research scientist at Columbia University’s Lamont-Doherty Earth Observatory, who was not involved in the research. “Areas like the Rockaways, Staten Island, are just not sustainable. They cannot exist in 100 or 150 years as they exist now.”

The study does not explicitly state that the changes are due to human activity but implies it “by the timeframes,” Horton said. The researchers wanted to compare recent decades to the period before the Industrial Revolution. “The climate community knows the conditions were different in the last 30 years than they were in the last 1,000,” he said.

Central Climate contributed to this report.