Don’t freak out about rising sea levels

Anthony Watts Meteorologist and Climate Blogger
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One of the more common visual tactics used by AGW proponents to scare people into thinking that AGW-induced sea level rise is a big threat is to show altered photographs and GIS models of a city near the ocean (take your pick, New York, London, San Francisco, etc.). These futuristic images demonstrate what the city might look like once global warming kicks in and kicks our butt, apparently without anyone noticing the advance of the sea. Take for example, Lower Manhattan, one of the more common targets. The top image is a future shock rendition from the History Channel “Armageddon Week” and the bottom image is a photo of present-day reality from Wikimedia.

Scary, huh? And it’s not just photos, now that most anyone with a PC can run Google Earth, there’s a veritable cottage industry of people who make sea level inundation KML files using the 3D buildings feature for major cities. It works very well to get people’s attention. But how much of a looming threat is it when compared to the reality of measured sea level rise? Let’s find out.

Will Manhattan really look like that in the future? You can even interactively freak yourself out here, at Climate Atlas, and see what it looks like in NYC when the entire Greenland Ice Sheet melts:


Well, I can see how people must be terrified. Just look at this plot of sea level rise at the Battery Park tide gauge from NOAA:

Yeah, it’s headed up, wayyyy up. 2.77 millimeters per year. So, to get the levels in the photo and 3D GE model shown above, we’d need to do some simple calcs.

The Google Earth 3D model is easy. It specifies a 3-5 meter sea level rise, so we’ll call it 4 meters.

For calculation purposes, we’ll assume sea level rise to be linear, and round up the Battery Park tide gauge rate to 3.0 mm per year, which puts it closer to the 3.1 mm per year measured by satellite and published at Colorado State University’s Global Sea Level Page.

4 meters = 4000 millimeters

4,000 millimeters /3.0 millimeters per year = 1,333 years

Now, how about the doctored image from the History Channel? There’s no reference given on the height of sea level rise on the web page, but fortunately, we have built-in yardsticks in the image. The story height of buildings in the photo can easily be estimated from the before and after photos shown at the top of this post.

I’ve selected the white building on the northeast side of Battery Park, along South St. I counted 18 stories of that building as being underwater using the hi-res image here, and I’ll estimate from other objects in the photo (like the water-to-pier-to-street height) that it is an additional two stories from street level there to the present day sea level (PDSL).

So what is the height of a story? The Council on Tall Buildings and Urban Habitat gives a handy guide on story height for office buildings like that one. They say that an office building like that one has a story height of 3.9 meters, so we’ll use that.

History Channel photo submersion = 20 stories

Story height = 3.9 meters

Sea Level Rise in the photo 20 x 3.9 meters = 78 meters

78 meters = 78,000 millimeters

78,000 millimeters / 3 millimeters per year = 26,000 years

26,000 years to get that? Would those buildings still be standing then? And even more important, wouldn’t we be in a new ice age by then? If we did enter another ice age, the sea level would be lower, as demonstrated in this graph below. Note the level 24,000 years ago.

This demonstrates the folly of assuming that climate change, and hence sea level rise, is linear. As we all know, it isn’t, yet that doesn’t stop many AGW proponents from using present-day measurements to project linearly into the future and then generate scary scenarios and visuals from it.

Even on the short-term, such predictions fail miserably. Take for example Dr. James Hansen of NASA GISS. Read his prediction 20 years ago about sea level rise in New York City, which I previously covered in a little known 20-year-old climate change prediction by Dr. James Hansen – that failed badly.

He said that [in 20 years]:

The West Side Highway [which runs along the Hudson River] will be underwater.

Problem is, here it is 20 years later, and people still drive that highway today without the use of Jet-Skis.

What got me started on this post was a comment left on my website, Watt’s Up With That?, by “Rascal”:

Copy the following address in to your browser, and observe the expansion of lower Manhattan since 1660.


Note that the West Side Highway (West Street) over half of the World Trade Center site, and the South Street Seaport were “under water” in 1660!

He’s right. And one thing many AGW proponents don’t consider (in addition to the non-linearity of climate change) is the adaptability of humans. For readers here, I’ve taken that Flash animation at Racontours.com and made it into an animated GIF below:

They write about this historical account of Lower Manhattan:

Based on our study of historical maps of Manhattan, Racontours has been able to create this simulation of the expansion of the island’s coastline. This topic is covered in both our South St. Seaport and Lower Manhattan tours, and most people are amazed at the transformation that’s taken place. Pearl St, named for the seashells that washed up there, once ran along the river. (Click here for a view of Captain Kidd’s house at the corner of Pearl & Wall Streets)

The first land reclamation was undertaken by Peter Stuyvesant upon taking over as the colony’s governor in 1646. Hoping to facilitate waste disposal and transportation, he organized the excavation of the canal along what is now Broad St. Back then, this was still called New Amsterdam, and the Dutch were great believers in canals.

By the American Revolution, the city’s population had grown to 30,000, and land had become scarce and cramped in the city center. That’s when the city began to sell ‘water lots,’ wherein entrepreneurs would seek to use landfill to create additional lots for use.

The most recent landfilled area led to the creation of Battery Park City, built in the 70′s on the earth excavated from the World Trade Center’s foundation.

Based on the 2.77 millimeters per year (call it 3 mm) of current sea level rise as shown by that Battery Tide gauge, in the 344 years (1660-2004) the sea level would have risen by:

344 years x 3 millimeters/year = 1032 millimeters or 1.032 meters.

Clearly, New Yorkers have been able to stay well ahead of that 1-meter rise since the city was founded.

The next time your friends get freaked out about sea level rise, or “high water,” show them this.

Mr. Watts operates the most visited blog on climate science in the world, www.wattsupwiththat.com now with over 61 million visits. He has spent 30 years on air in radio and television as a weather forecaster, and still does daily radio broadcasts. In 2007, he founded the surfacestations.org project, which with the help of volunteers nationwide found that only 1 in 10 of the weather stations used for monitoring climate in the USA met the government’s own standards for station siting quality. He also operates a weather technology business, embraces energy efficiency with solar power on his home and drives an electric car.