Caution: New Sea Level Story May be a Step too Far

April 21, 2016

Above, James Hansen’s recent statement to me re sea level rise.

No one is more deeply concerned about SLR than Hansen, and he has ventured some of the largest numbers we’ve seen for what the potential might be.  He does tell us that those numbers rest on certain assumptions:

“..Our record of precise knowledge of the changes in the mass of the ice sheets is rather short, it really began with the gravity satellite, which now has a record of only 12 years, but over that period the mass loss has increased rapidly …if it continues to double at the rate that it has in the last decade, then we could get, within 50  years, meter scale sea level rise, and you’d rapidly, within another one or  2 decades, get multimeter sea level rise. So that’s an enormous threat.”

So, multimeter sea level rise possible if his calculations are accurate, if his mechanism is real, and if the short record of accurate accounting is consistent decades into the future.
Those caveats should give us caution in assigning too much cred – yet – to the newest story on sea level being passed around.

Insurance Journal:

Think sea level rise will be moderate and something we can all plan for? Think again.

Sea levels could rise by much more than originally anticipated, and much faster, according to new data being collected by scientists studying the melting West Antarctic ice sheet – a massive sheet the size of Mexico.

Margaret Davidson, NOAA’s senior advisor for coastal inundation and resilience science and services, and Michael Angelina, executive director of the Academy of Risk Management and Insurance, offered their take on climate change data in a conference session titled “Environmental Intelligence: Quantifying the Risks of Climate Change.”

Davidson said recent data that has been collected but has yet to be made official indicates sea levels could rise by roughly 3 meters or 9 feet by 2050-2060, far higher and quicker than current projections. Until now most projections have warned of seal level rise of up to 4 feet by 2100.

These new findings will likely be released in the latest sets of reports on climate change due out in the next few years.

“The latest field data out of West Antarctic is kind of an OMG thing,” she said.

So there’s quite a bit of discussion among knowledgeable folks that this is overdoing it a bit, and the article cites no new research numbers to support the direst estimates.

Readers and viewers know that I’ve produced a number of videos on the issue and interviewed some of the best experts in the field – but I caution those tweeting this new meme around that, so far as I know, “the latest field data” cited here do not give us anything like 3 meters by 2050, and even Hansen’s worst case quoted above gives something like a meter by mid century, scary enough – with multi-meter rise more toward 2100.

So, plenty of reason for concern, but recall the kerfuffle with a stray sentence in the 2007 IPCC report, claiming that “Glaciers in the Himalaya are receding faster than in any other part of the world and, if the present rate continues, the likelihood of them disappearing by the year 2035 and perhaps sooner is very high.”

This statement turns out to have escaped the rigid review process, and became a talking point for climate deniers seeking to undermine the reports solidly based major conclusions.

So, bottom line, always look for specific published, peer reviewed sources for claims as important and sweeping as these. Sea level rise is already an emergency, but dealing with it means scientists and citizens have to maintain high standards for the information they rely on and disseminate.

UPDATE: Clarification from NOAA official quoted in article, to Eric Holthaus of Slate.
Right-clicking should get you a larger version.




42 Responses to “Caution: New Sea Level Story May be a Step too Far”


    The answer the scientists got is described in their paper in the dry language of science, but it could easily serve as the plot device of a Hollywood disaster movie. They found that West Antarctica, which is already showing disturbing signs of instability, would start to break apart by the 2050s.

    That is without factoring in the geothermal factor increasing the fluidity under the ice sheets encouraging more rapid flow


    Rapid bedrock uplift in the Antarctic Peninsula explained by viscoelastic response to recent ice unloading

    This results in a best fitting Earth model with lithospheric thickness of 100–140 km and upper mantle viscosity of View the MathML source6×1017–2×1018 Pas – much lower than previously suggested for this region. Combining the LARISSA time series with the Palmer cGPS time series offers a rare opportunity to study the time-evolution of the low-viscosity solid Earth response to a well-captured ice unloading event.

    Using a combination of inferred ice history, GPS and GRACE data, Ivins et al. (2011) suggested this region has a relatively thin lithosphere (20–45 km) and a low viscosity mantle (View the MathML source3–10×1019 Pas). Due to the low viscosity nature of the upper mantle, the Earth’s viscous response to ice-mass change in the AP is much more rapid than in other regions of Antarctica, and post-1995 unloading events may hence be contributing to the observed uplift in the NAP through viscoelastic rebound.

    Just another Positive feedback

    • So, the upshot from the paper is that the rate of rise due to unloading is about 1 cm per year.

      My reaction is that if, indeed, the mantle and bedrock are responding to ice unloading, I wonder what the nearfield gravity effect is on the ocean? That’s a non-homogeneous contribution to worldwide SLR, but it’s something. It certainly is an effect in the North, due to Greenland, where sea level near Greenland is actually decreasing as a result, but the water previously piled up due to gravitational attraction now adds to sea levels farther away.

  3. […] “Rationale: In January 2016, CRD Board Chair Barb Desjardins asked the Environment Committee to provide a report detailing how the region should respond to climate change. The Board Chair’s request is opportune. Recent evidence suggests that climate change is accelerating and poses an ever growing, potentially critical, threat to human society and all species on our planet. Only three years ago, generally accepted estimates indicated a maximum sea level rise by 2100 of about 33 centimetres or 1/3 of a metre. By 2015, these estimates had been revised to indicate a rise of about 1 metre. Recently, study of the West Antarctic ice sheet revealed deterioration at a much more rapid pace than expected causing researchers to suggest sea level rise of 2 metres by century’s end. A subsequent review of this data by the National Oceanic and Atmospheric Administration, a U.S. governmental agency in the Department of Commerce, concluded that a near 3 metre rise could be expected, quite possibly by 2050 – 2060 as described in the following quote: “. . . In a presentation at the Risk Management Society’s RIMS 2016 conference in San Diego April 12, a top scientific official with the National Oceanic and Atmospheric Administration said that recent, as-yet-unpublished data from Antarctica suggests that sea levels could rise three meters — almost ten feet — by the middle of the century. Margaret Davidson, NOAA’s senior advisor for coastal inundation and resilience science and services, told conference attendees that “the latest field data out of West Antarctic is kind of an OMG thing.” Davidson said that data shows sea level rise could reach three meters by 2050 or 2060, a much steeper rise happening far sooner than even the most catastrophic scenarios currently available in peer-reviewed journals and the far more conservative estimates published by the Intergovernmental Panel on Climate Change. That steep a rise in sea level would put significant parts of many California cities underwater in just two or three decades. . . .” These projections have yet to be fully reviewed and accepted by the broader scientific community. Nevertheless, if correct, they suggest a catastrophic outcome if serious mitigation does not occur very quickly. Severe environmental damage would almost certainly result. Equally alarming are the potential fiscal and social impacts. A three metre rise would eliminate, or put at severe risk, hundreds of trillion dollars of assets. Protecting them would be extremely expensive if it were possible at all. Meanwhile, society would likely face hundreds of millions of “sea rise refugees” as low lying coastal areas were inundated or became otherwise unlivable. Another metric is equally alarming. Delegates at the recent Paris conference on climate change agreed that society cannot exceed an absolute maximum of 2 degrees Celsius (C) warming without risking run away climate change. However, the conference also agreed that keeping warming to 1.5 degrees C would better limit damage and provide a much greater margin of safety. Subsequently, a researcher at Concordia University created a “climate change clock” to indicate when these targets might be reached. His answer: Without a substantial increase in efforts to mitigate, 1.5 C will be reached in about 15 years (2031) with 2.0 degrees being reached in about 26 years (2042). These dates suggest very short time lines to accomplish the paradigm shift that all communities, including our own, may well face. To date, our responses to global warming could best be characterized as incremental and slow. Given the likelihood we are facing an increasingly urgent crisis, we must consider the need for an immediate and much more massive response.” Here is a link worth checking out…it includes a short email between Margaret Davidson and Eric Rignot. […]

  4. […] Dit doet het ijs nog sneller smelten. Volgens klimaatwetenschapper Hansen zou dit kunnen leiden tot 3 meter zeespiegelstijging in 2100. Aanmerkelijk meer dan de 1 meter waar het IPCC vanuit gaat. Dit standpunt is nog […]

  5. rogerthesurf Says:

    Of course the catch is that in my country, the sea level rise is still stuck at 1.7mm per year which it has been since records began.

    (GEOPHYSICAL RESEARCH LETTERS, VOL. 31, L03307, doi:10.1029/2003GL019166, 2004)
    (RSNZ, 2010 )

    In spite of this people still seriously warn me that the (EPA) of the US Government seems to think that sea level has risen 10 inches since 1880.!! Mia Culpa!

    1880 to 2016 = 136 years. Times 1.7 mm per year is 231.2 mm. This is, strangely, 9.102 inches. Well, not quite 10 inches, but within a bull’s roar of being right.

    I live in the south pacific. Never heard of the islands disappearing that you mentioned and no refugees have turned up here yet.
    An individual from Kiribati once tried to become one but got sent home. Strangely enough the quota for imigration from Kiribati is generally not filled it seems.

    Its worth looking at the UN who has an interest in sea level rise one would think.
    Try here, well documented



  6. ecoquant Says:

    Okay, the problem regarding catastrophic SLR is that it isn’t directly related to warming. I mean it is, but it’s about delivery of warm ocean water to Antarctic sheet bases, and then it’s about how close to leaving the grounding line the sheet face is.

    A lot of Antarctica in the WAIS and at the PIG has a ridge at the edge, and then the interior is below the level of the ridge in height. Currently that’s ice-filled. Should that side of the lever melt away, mechanism is nothing-nothing-nothing and then the interior becomes buoyant.

    Both Eric Rignot and Richard Alley have animations tied to presentations and papers which present this.

    The point at which buoyancy is achieved is obviously generally controlled by warming, but the precise mechanism depends upon all kinds of complicated things like viscous forces and coupling by friction to the glacial valleys. It really needs and deserves deep modelling and, as I understand it, efforts are being made to to that.

    Sorry, I don’t have time to dig up references at the moment.

    The point is it’s nonlinear, and all we know is the more warming is applied, we are increasing probabilities.

    In other words, this may be on a long tail, but the tail has non-negligible mass and it is foolish to think things out there behave the same as those need the mode do, just less frequently.

    I’m no expert at this, but I have read and studied a lot.

    Dr Hansen’s concerns are based in part upon 2.5 mya (?) paleoclimate conditions where atmospheric CO2 was 400 ppm. I heard that from Dr Kathy Sullivan, former NOAA head, too.

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