The 500 year FUD about sea levels

Ah, once again in response to a fearmongering press release, we see the obligatory “NYC is flooded” photoshop trick.

But guess what? I’ve already debunked that photo as impossible for the time frame. More on that later after we do the math on the press release that prompted this.

First the press release, from the University of Copenhagen

Sea levels will continue to rise for 500 years

Rising sea levels in the coming centuries is perhaps one of the most catastrophic consequences of rising temperatures. Massive economic costs, social consequences and forced migrations could result from global warming. But how frightening of times are we facing? Researchers from the Niels Bohr Institute are part of a team that has calculated the long-term outlook for rising sea levels in relation to the emission of greenhouse gases and pollution of the atmosphere using climate models. The results have been published in the scientific journal Global and Planetary Change.

“Based on the current situation we have projected changes in sea level 500 years into the future. We are not looking at what is happening with the climate, but are focusing exclusively on sea levels”, explains Aslak Grinsted, a researcher at the Centre for Ice and Climate, the Niels Bohr Institute at the University of Copenhagen.

Model based on actual measurements

He has developed a model in collaboration with researchers from England and China that is based on what happens with the emission of greenhouse gases and aerosols and the pollution of the atmosphere. Their model has been adjusted backwards to the actual measurements and was then used to predict the outlook for rising sea levels.

The research group has made calculations for four scenarios:

A pessimistic one, where the emissions continue to increase. This will mean that sea levels will rise 1.1 meters by the year 2100 and will have risen 5.5 meters by the year 2500.

Even in the most optimistic scenario, which requires extremely dramatic climate change goals, major technological advances and strong international cooperation to stop emitting greenhouse gases and polluting the atmosphere, the sea would continue to rise. By the year 2100 it will have risen by 60 cm and by the year 2500 the rise in sea level will be 1.8 meters.

For the two more realistic scenarios, calculated based on the emissions and pollution stabilizing, the results show that there will be a sea level rise of about 75 cm and that by the year 2500 the sea will have risen by 2 meters.

Rising sea levels for centuries

“In the 20th century sea has risen by an average of 2mm per year, but it is accelerating and over the last decades the rise in sea level has gone approximately 70% faster. Even if we stabilize the concentrations in the atmosphere and stop emitting greenhouse gases into the atmosphere, we can see that the rise in sea level will continue to accelerate for several centuries because of the sea and ice caps long reaction time. So it would be 2-400 years before we returned to the 20th century level of a 2 mm rise per year”, says Aslak Grinsted.

He points out that even though long-term calculations are subject to uncertainties, the sea will continue to rise in the coming centuries and it will most likely rise by 75 cm by the year 2100 and by the year 2500 the sea will have risen by 2 meters.

http://dx.doi.org/10.1016/j.gloplacha.2011.09.006

Contact:

Aslak Grinsted, PhD glaciologist, Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen. +45 3532-5893, aslak@gfy.ku.dk

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First, there has been no evidence of accelerating sea level rise. Willis writes in a previous entry:

Does increased CO2 cause increased sea level rise?

Short answer, data to date says no. There has been no acceleration the rate of sea level rise. Sea level has been rising for centuries. But the rate of the rise has not changed a whole lot. Both tidal stations and satellites show no increase in the historic rate of sea level rise, in either the short or long term. Fig. 1 shows the most recent satellite data.

Figure 1. Change of sea level over time. Radar data from the TOPEX satellite. The light blue line is sea level with monthly anomalies removed. The interval between data points is usually ten days. The gray line is the 1993-2004 linear trend projected to the end of the timeline. Gaussian average using a 71-point filter. Photo taken at Taunovo Bay Resort, Fiji.

Up until about the end of 2004, there was little change in the rate of sea level rise. Since then the rise has slowed down. The average (dark blue line) does not stray far from the trend (black line) up until 1994. Since then, it is well below the projected trend (gray line). We were supposed to be seeing some kind of big acceleration in the sea level rise caused by increased CO2. Instead, we are seeing a decrease in the rate of sea level rise. So the first claim, that increasing CO2 will cause increased rates of sea level rise, is not supported by the evidence.

Note that I am not saying anything about the future. The rate of sea level rise might go up again. What we can say, however, is that there is no hint of acceleration in the record, only deceleration. The claim of CO2 induced sea level rise is false to date.

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Second, these guys can’t even show math that matches the claims. Since there appears to be no acceleration in the record, and the average rate is 3mm per year we get this for they year 2100, 89 years from now:

89 years x 3 mm/year = 267 mm or 26.7 cm by the year 2100

Compare that to:

Even in the most optimistic scenario, which requires extremely dramatic climate change goals, major technological advances and strong international cooperation to stop emitting greenhouse gases and polluting the atmosphere, the sea would continue to rise. By the year 2100 it will have risen by 60 cm…

Even if nature doubled the rate of sea level rise to 6 mm/year we still wouldn’t make it:

89 years x 6 mm/year = 534 mm or 53.4 cm by the year 2100

60cm by 2100? FAIL

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Third let’s have a look at that photo of NYC again, since I’ve covered it before:

Below is a repost of an analysis I did on Nov 28th, 2010 on a photo from this “NYC is flooded” photoshop trick set. Guess how long it takes to get the results shown in that photo?

Freaking out about NYC sea level rise is easy to do when you don’t pay attention to history

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.

New York City under a 3-5 meter rise in sea-level due to global warming. Source: Inhabitat.com

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:

Gosh.

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

4000 millimeters /3.0 millimeters per year = 1333 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 2 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, sea level would be lower, as demonstrated in this graph below. Note the level 24,000 years ago.

Image: Global Warming Art – click

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 on WUWT 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 under water.(which has been “updated” now, even with the update it still fails)

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

West Side Highway in 2007. Image: Wikimedia

What got me started on this post was a comment left on WUWT by “Rascal”

Submitted on 2010/11/26 at 7:46 pm

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

http://www.racontours.com/archive/coastline_anim.php

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) 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:

Flipbook of lower Manhattan harbor and city adaptation from 1660-2004. Images from Racontours.com

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)