Let’s try answering this question on Quora:
I doubt sea level rise will be the first way we’ll get badly hurt by global warming. I think it’ll be crop losses caused by floods, droughts and heat waves, and property damage caused by storms. But the question focuses on sea level rise, so perhaps we should think about that… along with any other ways that New York City is particularly susceptible to the effects of global warming.
Suppose you know a lot about New York, but you need an estimate of sea level rise to get started. In the Azimuth Project page on sea level rise, you’ll see a lot of discussion of this subject. Naturally, it’s complicated. But say you just want some numbers. Okay: very roughly, by the end of the century we can expect a sea level of at least 0.6 meters, not counting any melting from Greenland and Antarctica and at most 2 meters, including Greenland and Antarctica. That’s roughly between 2 and 6 feet.
On the other hand, there’s at least one report saying sea levels may rise in the Northeast US at twice the average global rate. What’s the latest word on that?
Now, here’s a website that claims to show what various amounts of sea level rise would do to different areas:
Details on how these maps were made are here. One problem is that they focus too much on really big sea level rises: the smallest rise shown is 1 meter, then 2 meters… and it goes up to 60 meters!
Anyway, here’s part of New York City now:
Here it is after a 1-meter (3-foot) sea level rise:
(Click to enlarge any of these.) And here’s 2 meters, or 6 feet:
It’s a bit hard to spot the effects in Manhattan. They’re much more noticeable in the low-lying areas between Jersey City and Secaucus. What are those: parks, industrial areas, or suburbs? I’ve heard New Yorkers crack jokes about the ‘swamps of Jersey’…
But of course, a lot of the city is underground. What will happen to subways and other infrastructure, like sewage systems? And what about water supplies? On coastlines, saltwater can infiltrate into surface waters and aquifers. Where does freshwater meet saltwater near New York City? How will the effect of floods and storms change?
And of course, there are other parts of New York City these little maps don’t show: for those, go here. But watch out: at first you’ll see the effect of a 7-meter sea level rise… you’ll need to change the settings to see the effects of a more realistic rise.
If you live in a place that will be flooded, let me know!
Luckily, we don’t have to figure everything out ourselves: the state of New York has a task force devoted to this. And as task forces do, they’ve written a report:
New York City also has an ambitious environmental plan:
• New York City, PlaNYC 2030.
Finally, let me quote part of this:
• Jim O’Grady, Sea level rise could turn New York into Venice, experts warn, WNYC News, 9 February 2011.
Because it looks ahead 200 years, this article paints a more dire picture than my remarks above:
David Bragdon, Director of the Mayor’s Office of Long-Term Planning & Sustainability, is charged with preparing for the dangers of climate change. He said the city is taking precautions like raising the pumps at a wastewater treatment plant in the Rockaways and building the Willets Point development in Queens on six feet of landfill. The goal is to manage the risk from 100-year storms—one of the most severe. The mayor’s report says by the end of this century, 100-year storms could start arriving every 15 to 35 years.
Klaus Jacob, a Columbia University research scientist who specializes in disaster risk management, said that estimate may be too conservative. “What is now the impact of a 100-year storm will be, by the end of this century, roughly a 10-year storm,” he warned.
They would rise from the waters at Throgs Neck, where Long Island Sound and the East River meet, and at the opening to the lower harbor between the Rockaways and Sandy Hook, New Jersey. Like the barriers on the Thames River that protect London, they would stay open most of the time to let ships pass but close to protect the city during hurricanes and severe storms.
The structures at their highest points would be 30 feet above the harbor surface. Preliminary engineering studies put the cost at around $11 billion.
Jacob suggested a different but equally drastic approach. He said sea level rise may force New Yorkers to pull back from vulnerable neighborhoods. “We will have to densify the high-lying areas and use the low-lying areas as parks and buffer zones,” he said.
In this scenario, New York in 200 years looks like Venice. Concentrations of greenhouse gases in the atmosphere have melted ice sheets in Greenland and Antarctica and raised our local sea level by six to eight feet. Inundating storms at certain times of year swell the harbor until it spills into the streets. Dozens of skyscrapers in Lower Manhattan have been sealed at the base and entrances added to higher floors. The streets of the financial district have become canals.
“You may have to build bridges or get Venice gondolas or your little speed boats ferrying yourself up to those buildings,” Jacob said.
David Bragdon is not comfortable with such scenarios. He’d rather talk about the concrete steps he’s taking now, like updating the city’s flood evacuation plan to show more neighborhoods at risk. That would help the people living in them be better prepared to evacuate.
He said it’s too soon to contemplate the “extreme” step of moving “two, three, four hundred thousand people out of areas they’ve occupied for generations,” and disinvesting “literally billions of dollars of infrastructure in those areas.” On the other hand: “Another extreme would be to hide our heads in the sand and say, ‘Nothing’s going to happen.’”
Bragdon said he doesn’t think New Yorkers of the future will have to retreat very far from shore, if at all, but he’s not sure. And he would neither commit to storm surge barriers nor eliminate them as an option. He said what’s needed is more study—and that he’ll have further details in April, when the city updates PlaNYC.
Jacob warned that in preparing for disaster, no matter how far off, there’s a gulf between study and action. “There’s a good intent,” he said of New York’s climate change planning to date. “But, you know, mother nature doesn’t care about intent. Mother nature wants to see resiliency. And that is questionable, whether we have that.”