Carbon Dioxide, Sea Level, And New York City's Happy Future

Humans optimistically believe that populations and economies will continue to grow without limit for centuries to come. The history of the Earth begs to differ. There is consistent relationship between between CO₂ concentrations and sea level which can not be ignored. Greenhouse gas concentrations like those we have now (almost 400 parts per million) are systematically associated with sea levels at least 9 meters (28.5 feet) above current levels.

By comparing reconstructions of atmospheric CO₂ concentrations and sea level over the past 40 million years, researchers based at the National Oceanography Centre, Southampton have found that greenhouse gas concentrations similar to the present (almost 400 parts per million) were systematically associated with sea levels at least nine metres above current levels.

[image left: New York City as envisioned after a mere 3 meter rise in sea level.]

[My note: The CO₂ level in the atmosphere is currently 393/394 ppm (parts-per-million) in the atmosphere.]

The study determined the ‘natural equilibrium’ sea level for CO₂ concentrations ranging between ice-age values of 180 parts per million and ice-free values of more than 1,000 parts per million.

It takes many centuries for such an equilibrium to be reached, therefore whilst the study does not predict any sea level value for the coming century, it does illustrate what sea level might be expected if climate were stabilized at a certain CO₂ level for several centuries.

Lead author Dr Gavin Foster, from Ocean and Earth Science at the University of Southampton which is based at the centre, said, “A specific case of interest is one in which CO₂ levels are kept at 400 to 450 parts per million, because that is the requirement for the often mentioned target of a maximum of two degrees global warming.”

The researchers compiled more than two thousand pairs of CO₂ and sea level data points, spanning critical periods within the last 40 million years. Some of these had climates warmer than present, some similar, and some colder. They also included periods during which global temperatures were increasing, as well as periods during which temperatures were decreasing...

The researchers found that the natural relationship displays a strong rise in sea level for CO2 increase from 180 to 400 parts per million, peaking at CO₂ levels close to present-day values, with sea level at 24 +7/-15 metres above the present, at 68 per cent confidence limits.

Although it has taken "many centuries" for a CO₂/sea level equilibrium to be reached during the last 40 million years, that delay doesn't mean that New York City is off the hook. Consider this graph from The Observed Increase in Oceanic and Atmospheric CO₂ and an Outlook for the Future by Pieter Tans, published in the journal Oceanography in December, 2009 (pdf).

Note: Not all emitted carbon dioxide goes into the atmosphere. Some of it is absorbed by the oceans, which leads to ocean acidification, and some of it is taken up by the terrestrial carbon sink (photosynthetic biomass). Thus total emissions are higher than shown in this graph (left scale). CO2 persists in the atmosphere long after anthropogenic emissions start declining.

Although for various reasons I incline to Scenario A, which shows emissions peaking well before 2050, this less "dire" scenario for atmospheric CO₂ also shows that carbon dioxide in the atmosphere remains above or near 400 ppm for five centuries after the peak. I'm guessing that's enough time for sea levels to stabilize at (at least) 9 meters above the current level. Even if I miss my guess, that should certainly be enough time for the sea to rise 5-6 meters on the way to an even bigger flood.

Therefore, we are entitled to conclude that sometime in the coming five centuries, and probably sooner rather than later, depending on how the Greenland and West Antarctic ice sheets respond to the warming, The City That Never Sleeps will be toast. The Big Apple is going to become the Big Moose Pie. Looking on the bright side, such sea level rise will certainly also wipe out Washington D.C., which I think we can all agree would be a good thing

But don't despair, you future citizens of Gotham. All is not lost. How about underwater nightclubs?

 

Comments

[John D]

I remember the Mayor of Norfolk Virginia being interviewed after Sandy. He was saying how he was pushing for billions of dollars in funding for a sea berm, as his city got hit hard. His reasoning was that he needed to protect the millions of dollars in new development in downtown Norfolk. I've been to Norfolk and the downtown is certainly spectacular with all the new hotels and businesses. My question is who the fuck would invest all that money in a flood zone? Only people that expect the government to come to their rescue I assume.

[Jim]

I do find it interesting that pretty much all the talk about warming just goes to 2100, as if it magically stops there. It's just that out conception of what's important stops there.

[Oliver]

Apologies Dave, but you really got me thinking today. (Plus ca change...)

Flooded NYC is a vivid example of the likelihood of major disruption owing to rising sea levels, but I would like to see a world map showing remaining landmasses after a rise of say a conservative 7 metres above the current level.

If these scientific projections are borne out, it seems pretty clear that there will be a helluva lot more than a wipeout of big chunks of this Eastern seaboard conurbation. Road and rail distribution networks worldwide will be decimated, while even sea routes will be hampered by hazardous new waters that would take a long time to chart (if anyone could be bothered to embark on such work) plus the elimination of some familiar ports. Power networks will similarly be disrupted. Bread-basket agricultural lands are sure to be inundated by salt water in various regions. Whole island nations in the Pacific will disappear below the surface. And so forth.

This will probably coincide with the end of the resource-starved grid anyway, and no amount of hope, prayer and quantitative easing will make one iota of difference to the outcome.

Of course, the rise will be relatively gradual year on year, so first we will have complaints from increasing numbers of householders and landowners about the failure of local authorities to provide adequate flood defenses, then angry outcries about insurance companies refusing to renew cover against flooding. Who knows when people will get it that the waters will keep rising for the rest of their lifetime and beyond.

I'm no doomer, but it is sobering that among all the talk of fossil fuel depletion and middle class impoverishment and ocean acidification and nuclear irradiation and collapsing food distribution and dangerous extreme weather via climate change, it is the displacement of millions of people by rising water (possibly including drowning events) that brings it home how we're on a one-way trip to a planet hostile to mass human habitation.

I can envisage that the money-blinded plutocracy will be buying up all the desirable mountain retreats in Colorado, Switzerland and elsewhere, in a vain attempt to preserve their genes.

[Brian]

So I was listening to some podcast recently that was discussing climate change and sea level rise, and the guy talking says something like "Okay, so some people figure that the ocean rises up, so what? We just move inland a mile or so. No big deal. Coastlines have been changing for thousands of years."

I'm shaking my head, thinking...
1) fucking clueless
2) never mind that we are talking, literally, hundreds of millions of people
3) never mind that we are talking about trillions of dollars of existing built capital that People would theoretically want to replace (houses, businesses, docks, cities, etc.) and for which there is unlikely to be any meaningful financing
4) never mind that there are already people living a mile or so inland who might not want to give up their existing property rights (well, this only applies where People have property rights, which, in the case of this much sea level rise would end up being, precisely, no place... fuck 'em... so forget this one...)
5) fucking clueless

Then I deleted the podcast and moved on to SportCenter, exercising my own dominant Free Will. ;-)

[Alexander Ač]

Oh yes, humanity can ignore a lot lot of important things... such as "going uphill downstairs" see this down-ward global warming escalator:
http://www.skepticalscience.com/graphics.php?g=47
.
Well yes, the latest "down-ward" trend is the longest, just wait till the cooling effect of aerosols evaporates...

Alex