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Nature sea level rise shocker: Coral fossils suggest “catastrophic increase of more than 5 centimetres per year over a 50-year stretch is possible.” Lead author warns, “This could happen again.”

By Joe Romm

"Nature sea level rise shocker: Coral fossils suggest “catastrophic increase of more than 5 centimetres per year over a 50-year stretch is possible.” Lead author warns, “This could happen again.”"


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Coral fossils in Mexican canal walls suggest a rapid increase in sea level 121,000 years ago.

The prestigious journal Nature is publishing important new research on “Rapid sea-level rise and reef back-stepping at the close of the last interglacial highstand” (subs. req’d, abstract below).  As Nature explains in a summary and author interview (subs. req’d):

Some consequences of climate change are already unfolding. Glaciers and ice sheets are melting, and sea levels are rising as a result. However, scientists aren’t certain by how much the rate of sea-level rise might accelerate; current predictions for increases until 2100 range from 0.3 centimetres to 1.4 centimetres per year. But Paul Blanchon, a geoscientist at the National Autonomous University of Mexico in Cancºn, and his colleagues have learned that a sudden, catastrophic increase of more than 5 centimetres per year over a 50-year stretch is possible. On page 881, they describe their discovery that a sea-level jump of 2-3 metres already happened about 121,000 years ago. Blanchon tells Nature how and why it could recur [see below].

In other words, the Nature study says that during the during the last interglacial (the Eemian) evidence now suggests sea levels rose 20 inches per decade for five straight decades — a roughly 8-foot rise in a half century.

The Eemian was some 2°C warmer than current global temperatures — we will exceed that over most of the second half of this century on our current emissions path (see “Intro to global warming impacts“).

The authors conclude bluntly:

In our warming world, the implications of a rapid, metre-scale sea-level jump late during the last interglacial are clear for both future ice-sheet stability and reef development. Given the dramatic disintegration of ice shelves and discovery of rapid ice loss from both the Antarctic and Greenland ice sheets, the potential for sustained rapid ice loss and catastrophic sea-level rise in the near future is confirmed by our discovery of sea-level instability at the close of the last interglacial.

This research amplifies the findings in a number of recent studies — and warnings from leading climate scientists — that sea level rise can occur much more rapidly than scientists thought just a few years ago:

And remember, many of those studies and estimates were made before the new recent projects that temperature rise this century may be 4°C to 5°C or more.

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. We cannot let it happen.

Here is an excerpt from the Blanchon interview:

How did you find out that sea levels had risen so quickly in the past?

We were studying fossil reefs along the Yucat¡n peninsula in eastern Mexico, looking for interruptions in the reefs’ development, when we found two reef crests. One crest was about three metres above the current sea level, the other six. Some event had clearly disrupted their growth, killing the lower reef first and, within 50 years, allowing the higher one to develop into territory that is now farther inland. One possible cause of such disruption is an earthquake, but we know the peninsula was stable in the reefs’ lifetimes. The only other possibility is a rapid sea-level jump of two to three metres, which would essentially have drowned the lower reef.

Did you have to dive to the ocean floor to study the fossil reefs?

No, a theme park has been excavated in the middle of these reefs, which are on land south of Playa del Carmen. There’s no other place in the world where reefs of this age are so exposed. From the excavations, we were able to reconstruct the reef’s internal structure in three dimensions….

What do your results mean for sea-level rises in the future?

This earlier ice-sheet collapse happened during an interglacial, when it was warm and there wasn’t a lot of ice around “” just as it is on Earth today. We’re assuming rapid ice loss from an ice sheet produced the jump in sea level, because it’s the only known process that could generate such a rapid increase. This could happen again.

You can read more in Andy Revkin’s NYT piece, where he characteristically quotes some researchers who believe that the authors have not made their case:

To determine the pace of sea-level rise in that period, Dr. Blanchon charted patterns of coral revealed in excavations at the resort. He said his work revealed a clear point where an existing reef died as the sea rose too fast for coral organisms to build their foundation up toward the sea surface. Once the sea level stabilized again, the same group of corals grew once more, but farther inland and up to 10 feet higher in elevation, a process known to geologists as backstepping.

Such an abrupt change from stable coral growth to death and a sudden upward and inland shift of a reef could only happen because of a sudden change in sea level, he said.

But in interviews and e-mail messages, three researchers who focus on coral and climate said that while such a rapid rise in seas in that era cannot be ruled out, the paper did not prove its case.

Daniel R. Muhs, a United States Geological Survey scientist who studies coasts for clues to past sea level, cited a lack of precise dating of the two reef sections. William Thompson, a coral specialist at the Woods Hole Oceanographic Institute, agreed, saying that given the importance of the conclusion, Dr. Blanchon interpreted the physical features without sufficient corroborating evidence.

[Note to Andy:  Where is the third critic?]

But Dr. Blanchon maintains that the work will hold up, saying the signs of abrupt change are etched in the rock for everyone to examine.

It is an interesting journalistic question as to whether straight science reporting on a new study needs such “balance.”  After all, the article passed Nature‘s rigorous peer review process.  That suggests the experts Nature chose to review it thought it was both accurate and important.

I would say it is perfectly legitimate to quote one or two scientists who question the results — but only if your story also points out that a number of other studies using very different methods have projected rates of sea level rise that are quite comparable (see links above).

Indeed, as I’ve previously noted, in 2007 a Nature Geoscience study looked at the last interglacial period (the Eemian, about 120,000 years ago) “” the last time the planet was as warm as it soon will be again.  That study found seas rose 1.6 meters (5 feet) per century “when the global mean temperature was 2 °C higher than today,” a rather mild version of where we are headed in the second half of this century.

So until and unless the journal or the authors publish a correction, this study serves as one more important warning from Nature and from little ‘n’ nature that we are risking unmitigated catastrophe if we don’t cuts emissions sharply and soon.


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28 Responses to Nature sea level rise shocker: Coral fossils suggest “catastrophic increase of more than 5 centimetres per year over a 50-year stretch is possible.” Lead author warns, “This could happen again.”

  1. A Siegel says:

    Thank you for this (terrifying) study news.

    This is a good example, for me, of the problems of resting our hats on the IPCC hook. The IPCC is a lowest common denominator, backward looking, conservative look at what might happen.

    Terrifying that we might be measuring sea level rise by the end of the century (if not by 2050) in terms of feet (or meters) rather than inches/centimeters.

  2. Mike D says:

    It’s not uncommon for paleontological papers to use preliminary radiometric dates from other studies. Happens all the time, even in bigtime journals like Nature. Usually it doesn’t matter because getting time resolution down to such a fine level isn’t that critical. I haven’t seen this paper but my first response was to question the dating also, and I’m no AGW skeptic. Not saying it couldn’t be accurate but claiming to resolve the date to within 50 years when you are looking at sediments from 120k years ago is pretty bold, especially if your results are entirely dependent on it. So I hope it’s well-supported.

  3. MarkB says:

    This wouldn’t be all that shocking, but it would be a bit surprising. Sea level rise has accelerated over the last century and particularly the last 30 years but not anywhere as dramatically as required to meet the rate implied by this study. The precise dating appears to be an issue.

    This reminds me…Contrarians often create a strawman about Gore’s Inconvenient Truth, claiming that he said we will have a 20-ft sea level rise this century. He was basing it off a likely scenario of part of the Greenland and Antarctic ice sheet contribution, but he clearly didn’t specify a timeframe on it. The pace that this study indicates might make their strawman come true.

  4. Leland Palmer says:

    Dunno about the methodology, but if this a valid result, we have to realize that this rapid sea level rise likely occurred without the sort of hugely accelerated release of greenhouse gases we are seeing at the current time.

    So, it could be faster this time, and likely will be.

    Our current CO2 and methane increases of 1% or so per year are just unheard of, in geological time, I think. These rates of release of greenhouse gases appear to be thousands of times the rate of natural processes.

    Our only hope, so far as I can see it, is for the spike in greenhouse gases to be so sharp, and decline so quickly, that the climate system does not have time to react catastrophically to these huge rates of change.

    I believe that this can be done using biomass energy plus carbon storage:


    James Lovelock realized in 2004 that the climate system is in failure mode. As probably the foremost expert in the world in the earth’s climate as a self-regulating system, how could we have ignored him?

  5. Bob K says:

    I’m with Dan Muhs on this one — the radiometric dates in their paper aren’t good enough to support an argument about timing, so their rate estimate is entirely dependent upon a qualitative ecological interpretation. Intriguing, but by no means conclusive.

    The most robust aspect of the paper is the identification of two distinct sea level highstands during the Last Interglacial, both significantly higher than at present, and consistent with work from several other localities.

  6. David B. Benson says:

    Whatever, I suggest hard work on ending burning coal. A simple substitute is to grow algae, convert to biochar and burn biochar in place of coal. Under ideal growing conditions (sunny locations) it should be possible to produce 40 t/ha/yr of biochar this way. Growing the algae in tanks means any ground will do, so any sunny wasteland ought to work.

  7. paulm says:

    Does anyone here really think that we are going to prevent multi-feet sea level rise by 2100?

    The only way we will be able to keep below 3dC is with a miracle happening like say massive volcanic activity or something out of left field.

    I think we have lost the Arctic ice cover which means we are moving to a new warmer climate state what ever mitigation we introduce. And that means multimeter sea level rise (and I am afraid the collapse of civilization)

  8. Rabid Doomsayer says:

    John Holdren spoke of a car driving towards a cliff in the fog with dodgy brakes. For a second the fog cleared, are we still on the road?

    We ignored the road closed sign, we ignored the bridge out sign last chance the truck arrest bed.

    No it is our right to use the bridge, the one that isn’t there.

  9. Harrier says:

    Actually, to me this speaks to the robustness of our biosphere. What if this means that not only sea level rise, but temperature rise has occurred on our planet at a much more dramatic rate in the past than we’ve previously believed? That would imply that life on Earth can weather strikingly fast shifts in global climate, and even do so without a large amount of extinctions.

    Still not good news for us, but better news for life in general, I think. As James Lovelock has said, “Gaia is a tough bitch.”

  10. ecostew says:

    I agree it’s going to take more research to confirm, but it doesn’t mean we shouldn’t be aggressive in mitigating AGW – just one more piece of scientific evidence.

  11. That would imply that life on Earth can weather strikingly fast shifts in global climate, and even do so without a large amount of extinctions.

    What you fail to mention is those previous abrupt climate changes were still an order of magnitude slower than our current climate change, and were not accompanied by seven billion human beings dependent upon carbon fueled widespread agriculture, hunting and gathering, and land development.

    You do the math. Then make the observations.

    It is not a pretty picture.

  12. hapa says:

    Actually, to me this speaks to the robustness of our biosphere. What if this means that not only sea level rise, but temperature rise has occurred on our planet at a much more dramatic rate in the past than we’ve previously believed?

    yeah, pretty amazing at geologic time scales. now reset the pieces, set new rules — it’s getting hotter faster, land and ocean are seriously damaged, and mass migration is pretty much off the table — and if you get the same “better news for life in general” result, you win.

  13. hapa says:

    ooooooh. spooky.

  14. Harrier says:

    50 years isn’t geologic time. If the study is right, my point stands.

  15. Gail says:

    Lovelock is overly optimistic. He fervently believes the Anglo-Saxons will survive, due to location and genetic superiority, and advocates nuclear power because he doesn’t want wind farms to disturb the pastoral views from the grand estates of the nobility.

    He’s almost the English Freeman Dyson.

  16. David B. Benson says:

    Harrier — I assure you that the temperature change during the Eemian interglacial was slow, but steady; ice core data confirms this. What this paper suggests is that the response of GIS and WAIS to this temperature change was highly nonlinear; I find this quite credible.

  17. hapa says:

    harrier: you were saying that a half-century flood — and a relatively small change by interglacial standards — didn’t trigger extinction, right? so i thought you were talking about the consequences in later years or something. it doesn’t seem to me like a quick burst upward in a long rising trend would’ve demolished anybody.

    today’s situation is much more stressful. the extinction event, when people of the future lay it all out, they may point earlier than the industrial revolution to locate its start. rapid warming is pain-on-pain.

  18. ecostew says:


    So what happened during these events and do we want our children and the 7th generation to experience AGW and its intensification?

  19. Sasparilla says:

    As A Siegal said, “Thank you for this (terrifying) study news.”

    While I had read of more rapid sea level rise projections recently, ~8 foot rise in 50 years would literally be a catastrophe for our societies to deal with. Joe said these kinds of numbers are coming from other scientists from unrelated studies, which makes is much scarier.

    The rate at which we keep finding out how much deeper the hole is we’re digging for ourselves and how much faster than anticipated these changes are happening is staggering. The fact that all this seems to be continually accelerating (as the science tries to catch up with what the scientists are observing) over the years without apparent letup is extremely frightening.

  20. paulm says:

    Yes Aasparilla,

    Whatever the scientist say today is out of date, usually within 6 months.

    So taking that as is, I would expect a big sea level rise jump between 2015 – 2020, probably of several inches.

  21. paulm says:

    “John Holdren spoke of a car driving towards a cliff in the fog with dodgy brakes. ”

    Rabid Doomsayer,
    Its worse than that….

    Its a truck craning towards a cliff, down hill… and there’s ice on the road.

  22. caerbannog says:

    Actually, to me this speaks to the robustness of our biosphere.

    This is rather like a chef saying to the lobster, “this speaks to the robustness of the pot and stove.”

  23. jorleh says:

    Is Washington Post going to put this new information on it`s front page?

  24. Chris S says:

    With regard to the robustness of the biosphere.

    It should be noted that one of the major ways species adjust to change is through dispersal – as evidenced (for example) by insect species now known only from Siberia found in glacial deposits in the UK.

    There is, however, a major problem with this in today’s world – habitat fragmentation. It is practically impossible for many (most?) species to utilise the contiguous habitat that has existed through major climate episodes of the past. Agriculture, urbanisation, mining, land reclamation and other anthropogenic land-use changes have effectively corralled the natural world across many parts of the globe.

  25. paulm says:

    Ouch Joe. Things are looking bad. Scary thread.

  26. lgcarey says:

    One of the comments at the Dot Earth blog regarding this study has given me “the willies” and I’d appreciate it if anyone who knows more about the cryosphere than I do has any thoughts – the author describes this event as the beginning of “a century of climate havoc” about 120 kya. Basically, in his post David Stoney points to a 1995 Scientific American article that discussed research on limestone deposits in the Bahamas that found basically the same abrupt sea level event — a rapid twenty foot sea level about 120 kya, during a climate regime similar to today’s in terms of temp, CO2 and sea level. However, it appears that the sea level then plunged 50 feet — these events all seem to have occurred within the space of only a century or so and were immediately followed by the onset of the last ice age.

    The post is here: http://community.nytimes.com/blogs/comments/dotearth/2009/04/15/do-old-corals-hint-at-fast-sea-rise.html?permid=72#comment72
    The text of a related 1998 article from Earth Island Journal is here:

    I am reminded of Wally Broecker’s comment about climate being an angry beast and us busily poking it with sharp sticks.

  27. paulm says:

    There have been a few studies that have indicated a rapid rise of sea level.

    Coral reef clue to fast sea rise

    Most scientists believe it was a gradual rise over the past 9,000 years. But the existence of relic mangroves 70cm (27in) below the floor of the Barrier Reef, some with leaves and branches still intact, suggests an abrupt rise.

    Dan Alongi, a biologist at the Australian Institute of Marine Science, said it appeared that sea levels rose about 3 metres in less than 30 years, drowning forests and flooding estuaries, 20 times faster than previously thought.

  28. Jimmy says:

    I would like to point out that rock and soil (sometimes entire continents) shift, carrying any objects inside them. However, if the land containing these fossils did not shift this proves that fossil fuels are not responsible for ‘climate change’ because 121,000 years ago people were burning thousands of gallons of diesel fuel to ship ‘green’ cars, assembles in a factory in China that used copious amounts of diesel fuel, wich were shipped using more diesel fuel from Saudi arabia, across the pacific.
    In fact, I doubt people were burning any fossil fuels 121,000 years ago.