The anticipated paper by J. Hansen, M. Sato, P. Hearty, R. Ruedy, M. Kelley, V. Masson-Delmotte, G. Russell, G. Tselioudis, J. Cao, E. Rignot, I. Velicogna, E. Kandiano, K. von Schuckmann, P. Kharecha, A. N. Legrande, M. Bauer, and K.-W. Lo, called “Ice melt, sea level rise and superstorms: Evidence from paleoclimate data, climate modeling, and modern observations that 2◦ C global warming is highly dangerous“ (Atmospheric Chemistry and Physics Discussions, 15, 20059–20179, 2015) is now available. I have updated my listing of the related articles.
Hansen’s team posits and offers evidence for a non-linear feedback between ocean temperatures and ice mass loss, among other effects, characterizing it in terms of possible doubling times. Comparison with and calibration against paleoclimate evidence, climate models (with corrections), and current observations indicate that Eemian sea levels may be seen within a century. There are other effects related to storms as well.
Professors Gavin Schmidt and Kevin Trenberth, also major climate scientists, have commented that the Hansen, et al study explores physical possibilities, but they don’t designate it as mainstream, or expected, suggesting things could go this way, but it would be really bad luck. Schmidt, at least, does not believe the report or possibility will move the needle on the upcoming UNFCCC global talks in September and December, in Paris.
As some are fond of saying, Professor Hansen may seem alarmist, but he’s also been right quite a number of times, including estimates of climate change and global fossil fuel consumption which to the rest of us look like educated guesses.
I’d love to read an assessment by Professor Ray Pierrehumbert. We’ll see.
But if Professor Hansen and colleagues are right, there’s going to be some massive loss of wealth, especially in developed countries over the next couple of decades. (See also Hinkel, et al, “Coastal flood damage and adaptation costs under
21st century sea-level rise“, although those costs understate those which would be incurred should the Hansen, Sato, and colleagues scenarios play out.) The sad thing is, whatever Hansen, Sato, and colleagues, including Professors Ruedy and Rignot, say, it appears we’re going to do the experiment to find out.
25th July 2015
Comments on the Hansen, Sato, et al paper, from the University of Colorado’s Tad Pfeffer, interviewed by Andy Revkin of The New York Times.
Also, Ken Miller’s “Sea-level Change: Past, Present, and Future”
By the way, that presentation was at a chapter of the American Association of Petroleum Geologists, which, although I applaud, is kind of weird.
Update, 26th July 2015
“… the tiger lurking around the corner at your next turn isn’t absent because you can’t see it.”
I posted the following comment pertaining to the Hansen, Sato, Rignot, et al paper in response to a posting on Google+ by Bill Smith:
It has long been asserted that the IPCC reports underplayed risks of catastrophic sea level rise. There is no accusation of malfeasance or anything in that statement, simply an acknowledgment of the limitations of the IPCC process. It is, after, kind of a large review paper, or, worse, metastudy and, accordingly, it can only convey what’s been published and peer reviewed. Given that the peer review process introduces serious lags, and the IPCC review process closes the books a dozen or so months before publication, what you get in IPCC is reports which can lag the science by 3 years, often more. Then, paywalls impede further progress. Given any particular field, whether geophysics or oceanography or, mine, statistics, the people practising don’t wait for peer review to read and study these papers. That’s one of the reasons why people read arXiv.org and other open source forms, like the journal where Hansen, Sato, Rignot, and company decided to publish their paper. This is severe enough that now, the NIH insists any paper funded by their dollars *must* be made publicly available for free within a short time after publication.
Still, the idea of “Mass Extinction” for human beings is extremely unlikely. A collapse of civilization, while highly improbable, is in the cards. And, in the case of catastrophic sea level rise, the principal losers would be coastal property owners. Moreover, even in the catastrophic mode, it would be slow enough that people could readily get out of the way. It’s not like a storm.
I think the problem with the Hansen, Sato, Rignot, et al paper, which I read, is that there is no viable mechanism proposed which could cause the sea level rise to be so fast. There is evidence it has risen quickly in the past. Worse, and this is key for many of the critics, there is no way, given the paper’s methods, to (at present) quantify the likelihood of less than 1 century multimeter sea level rise compared with several centuries for the process. I think few disagree with the prospect that in 3-4 centuries, we’ll see multimeter sea level rise, especially if we remain on anything like our present course. Worse, that looks like it’s not reversible, and there is no technology that can reverse it, since it involves removing heat from the oceans, something that won’t happen even if we could magically bring atmospheric CO2 back to preindustrial.
The scientific community is bound to judge Hansen, et al by their own internal standards. I respect that. But, as someone often engaged at the interface between scientific inquiry and decision-making, the Hansen, et al result really ought to be picked up by some other group with the charge to fix that missing element. There isn’t any such group at present. Nor, with the funding picture, is there likely to be.
If policymakers want a deliberate smoking gun on this, Hansen, Sato, Rignot, and company won’t give it to them, and the scientific critics are correct that it does not help. However, the policymakers don’t seem to be up to doing what the mainstream scientists have told them — zeroing emissions by 2050.
We don’t have any definitive understanding which would allow prediction of timescales, but there are the potential for nonlinearities in this dynamical system which could lead to very scary outcomes. Prediction of such phenomena are, with present allocations of focus and financial resources in climate science, impossible. Nevertheless, the tiger lurking around the corner at your next turn isn’t absent because you can’t see it. I think the tone and message of Hansen, Sato, Rignot, et al is that we are wading into waters with huge lack of respect for the dragons that might lie beneath, and our intellectual history and sciences say they could very well be there. Human behavior in this regard is at present antithetical to anything which could be called prudence.
We’re going to find out by lighting a match to the container which contains something we know little about.