This is what a 2.8-metre storm surge did Emile Wamsteker/Bloomberg via Getty Images

There’s good news and catastrophically bad news for New York City.

The good news is that hurricanes might become more likely to miss the city over the next three centuries. This means that, relative to whatever the local sea level is in the future, the risk of huge storm surges could be lower than it is today.

However, the catastrophically bad news is that if we don’t slash greenhouse gas emissions, local sea level will rise by a huge 13 metres or more. With this added in, New York could be facing storm surges of more than 15 metres above the current sea level by 2300.


“Sea level rise itself is a very big hazard, before you start to look at tropical cyclones,” says Andra Garner of Rutgers University, New Jersey, part of a team behind the study.

The scary number is not a forecast. Rather, the study looks at a range of possible future scenarios, says Garner, including the business-as-usual emissions path we are still on. The 15-metre storm surge heights would occur on average once every 500 years in this scenario. If emissions are significantly cut, a 1-in-500-year event would produce only a 5-metre surge.

Ever more floods

Garner and her team used climate models to simulate the paths of future hurricanes and what size storm surges they will produce. These were combined with the latest sea level rise estimates.

They conclude that 2.3-metre floods, which happened in New York on average once in 500 years before 1800, struck roughly every 25 years from 1970 to 2005, and will typically happen every five years by 2030 to 2045.

If we don’t slash emissions, local sea level could permanently exceed 2.3 metres before the end of the century.

If these estimates of sea level rise seem high, it is because they are based on a study last year that concluded the Antarctic ice sheet could melt much faster than previously thought. Glaciologists say even these alarming new figures may be an underestimate.

Garner’s team also accounted for the fact that sea level rises at different rates around the world, and will be particularly high on the US East Coast.

Believe it or not

Any New Yorkers inclined to disbelieve the findings might want to consider that these don’t even represent the worst case – the seas could rise even higher. What’s more, the study looked only at hurricanes, not extratropical storms like Superstorm Sandy, which was no longer a hurricane when its 2.8-metre storm surge flooded New York in 2012.

Last but not least, a climate with stronger storms means a rare event could still devastate New York, even if such storms normally miss the city.

And New York has it relatively easy. The rest of the East Coast faces even bigger storm surges.

“The result is peculiar to New York City,” says team member Kerry Emanuel of Massachusetts Institute of Technology. “Almost everywhere else, including Boston, we see an increase in surge heights and storminess.”

If that wasn’t bad enough, meteorologist Jeff Masters of the Weather Underground thinks the good news part could be wrong. At least one study has concluded that climate change will make hurricanes more likely to head for the north-east, he points out.

“It is very likely that climate change will change the steering currents for hurricanes, resulting in fewer impacts in some regions and more in others,” says Masters. “Exactly how they will change is still very uncertain.”

Journal reference: PNAS, DOI: 10.1073/pnas.1703568114