Sea Level Rise at 20 Inches Per Decade?

By Chris Mooney | April 16, 2009 1:19 pm

According to Joe Romm, blogging a recent Nature study, that’s what’s possible–or at least, it appears to have happened in the planetary past, some 121,000 years ago. The numbers, Romm notes, translate into an 8 foot rise over 50 years.

How could such a quick increase in sea level happen? Well, the collapse of a massive ice sheet might do it. And when might that happen? Nobody knows.

As this discussion underscores, by far the greatest threat from global warming is catastrophic sea level rise. Yet given our current understanding of ice sheet dynamics, it’s also a very poorly understood risk. Still, if there were ever a time to err on the side of caution, this is it. Romm writes:

If sea levels were even 3 feet higher in 2100 (let alone 5 or higher) and rising 1 to 2 inches a year at that point, it would be the single greatest preventable catastrophe in human history.

All those who worry about the risks to the “economy” if we take climate action now, here’s a thought for you: What happens to the economy if coastal cities and major financial centers have to retreat from rising seas?


Comments (21)

  1. I agree; sea level rises may be the most pernicious and devastating effect of climate change. These figures look eminently scary.

  2. Jon Winsor

    One thing I’m surprised you don’t hear more about is the impact on agriculture.

  3. marty

    The amount of water on earth hasnt changed since the crust cooled. So where is this extra water comming from? Magic? Even a 2,000 year old Greek named Archemedes figured it out.

  4. Jon Winsor

    Marty– You would have a point if 1) the ice was already in the water, 2) water didn’t expand slightly when warmed.

    There are two ways of changing sea level on the human time scale. We can change the amount of water in the oceans, or we can make the water there is occupy more or less volume. The first corresponds to changing the mass of ice on land. The second can be done by warming or cooling the ocean. Colder water is denser, so the same mass of water occupies less space.

  5. Brian M

    Worried about the economy if we take a stand on global warming? Only because it’ll make no difference. If you’ll do a Google search you can find the percentage of greenhouse gas contributed by all human activity. Comes to about .28 percent. THat’s it. A little more than one quarter of one percent. So, if we reduce our contribution by half, what good will that do? Show of hands? Anyone? Answer — no good at all. Europe imposed an onerous, economy blasting cap and trade system, a lot like what Obama wants to impose on us, and it’s made no difference in their carbon footprint. So, yes, I worry about destroying our economy for no reason.

  6. Erasmussimo

    Brian, your argument is not logical. You are arguing that a number that is teeny-tiny is not significant. Here’s an example of why you’re wrong: whaddya say we inject just a tenth of a gram of neurotoxin from one of the most dangerous snakes in the world into your veins? It’s just a teeny-tiny little tenth of a gram, a bit more than one millionth of your total mass. It shouldn’t have any effect at all, should it? 😉

  7. Jon Winsor

    Brian– Coby Beck addresses that here:

    Anthropogenic GHG’s is small compared to overall natural production, but it’s cumulative…

  8. Brian M

    Erasmussimo – Talk about an illogical argument. First it’s argued that global warming increases in proportion to the amount of greenhouse gas present then you switch gears and say a teeny-tiny amount is very significant. Apples and oranges. Stay on point. Jon — Beck’s argument is a valid point but he’s only looking at carbon release into the atmosphere. Yes, we’ve influenced total carbon load but I was referring to total greenhouse gas load. And once you add in all the elements of the atmosphere with greenhouse influence — even water vapor has a significant greenhouse affect and humans contribute literally zero of water vapor on a global scale — human contribution still amounts to an incredibly small, and negligable, percentage.

  9. Jon Winsor

    even water vapor has a significant greenhouse affect and humans contribute literally zero of water vapor on a global scale

    You need to read this Coby Beck article:

    I bet you have other standard arguments from the rumor mill as well. Check through Mr. Beck’s other articles to get them addressed:

  10. What happens to the economy if coastal cities and major financial centers have to retreat from rising seas?

    Interesting question! A quick Google search for “manhattan real estate total value” gives about $200 billion for Manhattan, which seems to me to be about the right ballpark.

    200 billion dollars is a lot, but it wouldn’t be the end of the world. Moving all the stuff that happens in New York to Chicago would be expensive, but wouldn’t cripple the economy.

    RE: the rapid rise in sea levels 121,000 years ago: anybody know if there was a corresponding rise in extinctions and/or decrease in species diversity?

  11. Erasmussimo

    Brian, your number is the amount of carbon flux through the atmosphere: how much stuff is going into the atmosphere and coming out. There’s lots going in and lots coming out. The trick is that, if you increase the amount going in by just a tiny amount, and don’t change the amount coming out, then you get a cumulative effect. And in fact, the number that affects climate change is NOT the flux number you cite, but the concentration of CO2 in the atmosphere, which is most certainly increasing; it has increased by roughly half in the last 100 years. And THAT number is nothing to sneeze at.

    Gavin, it’s true that we could survive the relocation of New York City, but what about London, Amsterdam, Boston, Miami, Los Angeles, Portland — every port city on the planet. How much do you think that would cost us? More important, wouldn’t it be more cost effective to head that off now with some expenditures?

  12. More importantly, what about the developing and poor countries? What would happen if the 150 million people in Bangladesh or the millions in Shanghai or Bombay were displaced? It’s not just about displacing financial centers, it’s about displacing and accommodating large populations and all the problems that accompany such displacements. It’s not like space is not a problem in the world.

  13. 20 inches per decade means 5 meters in a century. To get that, you have to completely collapse either the Greenland ice sheet, or the West Antarctic Ice Sheet. (Or half of each, etc.) Doing so is not implausible. Doing so in only 100 years, even after the discoveries of the last few years, still seems on the very implausible end. Half that looks unlikely, though not unreasonable.

    My copy of Nature hasn’t arrived yet, so I have to wait. The publicly available figures, though, with the dating and its uncertainties, is short of nailing down a stunningly short period for the 3 meters of sea level change at 121 kya. Anything up to a couple of thousand years is possible, considering just those dates. When I do get my copy of Nature, I’ll blog about it as sea level and paleoclimate are interests of mine. In the mean time, 3 meters across 3000 years (to make the math easy) would only be 1 mm/year. We’ve averaged about 2 for the last century (3 meters in 1500 years).

  14. Erasmus:

    I have no idea if it would be more cost effective to spend money now to fight global warming or spend money later to deal with the consequences.

    I don’t think anybody knows that with any certainty– there are lots of unknowns. For example: will there be a cheap and effective geoengineering solution? How far, and how fast, will the oceans rise? What discount rate should we assign to money spent now versus money spent in the future? Should we assume long-term economic growth continues as it has for the last 50 years? If we spend money now will that make the long-term global economic growth rate increase or decrease?

    That’s all even before considering the really hard questions, like figuring out whether or not spending X billion dollars on CO2 reduction is a more effective environmental policy than spending those same dollars on habitat protection. Or poverty reduction. Or family planning.

    Maybe the best we can do is lock our best scientists and economists in a room and not let them out until they come to a rough consensus on how we should proceed. But even if we did that, is there any hope that their recommendation would be accepted by the politicians?

  15. Orson

    I’m calling out THIS one as junkscience. First, coral resolution is centuries, not decades. Second, where is the independent confirmation for rates of warming at such high levels? It doesn’t exist. As we know from he last Ice Age’s transitioning into the Holocene, the maximum rate of sea level rise is only inches per century.

    Thus, clearly politics is the deciding factor in getting this study published at Nature: gimme my global warming scar graaaaqavy-train, man!!!

  16. Erasmussimo

    Orson, if you wish to write a paper challenging the results of the Nature paper, that might well be a contribution to science. Perhaps, however, you should read the Nature paper first. Remember, we’re relying on indirect representation here and the conclusion of 20 inches per decade is prominently marked with a question mark. I’m certainly not taking this as proof. But I do think that the possibility is so serious that it deserves serious consideration. We’re keeping an eye out for errant asteroids that might hit the earth, even though the likelihood of such an event is microscopic.

  17. Apart from glacier melting and water expansion, what other major factor contributes to sea-level rise? That should be a good indication of warming.

  18. Orson

    So much of AGW “science” is reasonable ‘if…” provided “such and such” happens, and if what so-and-so claims is true. (but which we don’t yet know to be true)…

    Erasmussimo says …I do think that the possibility is so serious that it [the paper above] deserves serious consideration And your impression is reasonable and different from my above generalization exactly how? (We are talking a single study here from a once August outlet now reknown for its topical sensationalism.)

    LET’S just throw out Occam’s Razor and criteria like “extraordinary claims require extraordinary proof” while we’re at it!

    Oh, and well-documented facts like “there is an global warming alarmist establishment” as found by Richard Lindzen (SEE his ERICE Seminars paper from last August) and Christopher Horner’s November book “Red Hot Lies.”

    Obviously, I’m just full of unreasonable, unfounded skepticism. Dismiss me.

  19. In his book “The Black Swan: The Impact of the Highly Improbable”, Nassim Taleb expounds upon the dangers of low-probability events that can have catastrophic consequences beyond control. The recent financial crisis was a black swan that the smart math geniuses on Wall Street ignored. Black swans admittedly are game changers. We don’t want to fly a plane when we are not prepared for thunderstorms. We don’t want to discount the possibility of sea-level rises when the consequences could change the whole world for the worse. We would want to err on the safer side, just as we keep our seat-belts fastened at all times in a flight even when turbulence is mild.

  20. Erasmussimo

    Orson, you claim that Nature is a “once august outlet now renowned for its topical sensationalism”. I don’t think you can back up that claim. Have subscriptions to Nature decreased? Have references in other papers to papers published in Nature diminished? If you cannot offer any objective evidence to support your claim, I think it entirely fair and proper to dismiss it.

    Next you insinuate that a due regard for risk constitutes a rejection of Occam’s Razor. Here you confuse acceptance of a hypothesis with provision for the unlikely case where the hypothesis turns out to be true. I accept that the hypothesis is unlikely to be true. However, let me walk you through the proper way to evaluate risk. (Ashutosh discusses this issue in his response but I want to show you the specifics.)

    Suppose that the probability of catastrophic rise in sea level is 0.001. Suppose further that the cost that would be imposed by such a catastrophic rise in sea level would be $100 trillion. Then we can conclude that the expectation value for the cost of this hypothesis is $100 billion, and it would be rational to spend that much money to obviate that outcome.

    Of course, my numbers are all imaginary, but we can certainly agree that the cost of a catastrophic rise in sea level would be very high, and that the probability of such an event is non-negligible. So although we do not have the numbers, the evidence I see here convinces me that further research into the matter is justified, and that it already constitutes an argument in favor of some degree of reduction in CO2 emissions.

    Lastly, you make another claim: that it is a well-documented fact that there exists a global warming alarmist establishment. I have read Dr. Lindzen’s claims on this matter and I find them not merely unconvincing, but irrational. While I continue to respect Dr. Lindzen’s expertise in climatology, I dismiss these claims of his as ravings. In any case, I do not dismiss you. I dismiss the statements you made in your post this morning.


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About Chris Mooney

Chris is a science and political journalist and commentator and the author of three books, including the New York Times bestselling The Republican War on Science--dubbed "a landmark in contemporary political reporting" by and a "well-researched, closely argued and amply referenced indictment of the right wing's assault on science and scientists" by Scientific American--Storm World, and Unscientific America: How Scientific Illiteracy Threatens Our Future, co-authored by Sheril Kirshenbaum. They also write "The Intersection" blog together for Discover blogs. For a longer bio and contact information, see here.


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