abrupt and irreversible?

So the AR4 synthesis is out. You can read the SPM and cherry-pick your favourite bit. The BBC has, and has selected climate change is “unequivocal” – fair enough but boring, because we’ve had that already – and may bring “abrupt and irreversible” impacts which made me sit up and take notice.

There is a headline that sez this, “Anthropogenic warming could lead to some impacts that are abrupt or irreversible, depending upon the rate and magnitude of the climate change.” But what is the supporting text? “Partial loss of ice sheets on polar land could imply metres of sea level rise, major changes in coastlines and inundation of low-lying areas, with greatest effects in river deltas and low-lying islands. Such changes are projected to occur over millennial time scales, but more rapid sea level rise on century time scales cannot be excluded.” Its a looooooooonnnggg jump from “cannot be excluded” to “may”, even if you go via “could”. The next para has “The MOC is very unlikely to undergo a large abrupt transition during the 21stcentury.” so that doesn’t help you either. The factsheet doesn’t mention abrupt.

Conclusion: still no good backing for use of “abrupt”.

A bit lower down they note that One declaration that reportedly caused heated discussion during the week-long talks here states that climate change may bring “abrupt and irreversible” impacts. Well I should hope so too, because that headline seems to be very poorly supported indeed.

Postscript: the beeb further report Mr Ban urged politicians to respond at a UN climate change conference in Bali “Today the world’s scientists have spoken clearly and with one voice,” he said. “In Bali I expect the world’s policymakers to do the same.” which wins him the Nobel prize for naivety (well I don’t suppose he is naive enough to belive it; he’s just jollying people along in a way that chairs are expected to). Mr Ban arrived at the IPCC meeting in Valencia from a fact-finding trip to Antarctic and South America. “I come to you humbled after seeing some of the most precious treasures of our planet threatened by my own GHG emissions” he said. Can you spot the bit that he *didn’t* say ;-)?


  1. #1 Alexander Ač


    while it is not clear, if the “abrupt” and “irreversible” climate change can be tracked in the Synthesis, abrupt and irreversible changes in global carbon output *can*. Why should one emphasise something what is not written there, and not to emphasise on what *is* there? Is not the peak in global C output in 2000 – 2015 and the subsequent reduction in 2050 by 50-80% shocking enough? ;-)

    By the way, IPCC seems to be out-of-date for 3 reasons:

    Canadell et al. – sooner than expected slow-down of biosphere C uptake

    Holland et al – faster than expected summer artcic sea-ice decline (not to mention 2007)

    GlobalCarbonProject – faster than expected economic growth in China…

    and possibly forth reason – lower than expected public awareness :-)

  2. #2 Alexander Ač

    What about this? http://afp.google.com/article/ALeqM5iggsAV8wEXjxCt-QucSew1khh_oQ

    …chief French delegate Marc Gillet told AFP.

    Human activities “could lead to abrupt or irreversible climate changes and impacts,” the agreed text said.

    so “could” is better than “may”? ;-)

  3. #3 ciel

    and may bring “abrupt and irreversible” impacts

    I would point out that “abrupt and irreversible” is relative. On geologic time scales, the irreversible impact of, say, species extinctions, occurring on the order of a few centuries or even less and directly or indirectly caused by AGW, is, truly, a strong example of an “abrupt and irreversible” impact!

  4. #4 Hank Roberts

    William, have you any word from these people?
    Four or five years ago they predicted a change that might be relevant to this; they were quoted here:
    © British Antarctic Survey

    “The atmosphere is changing, and one of the key changes is that the ozone layer is getting colder. And when it gets colder, particularly during the winter, we can get clouds actually forming in the ozone layer, and these clouds are the key factor.
    … It’s getting colder because of the greenhouse gases that are being liberated by all the emissions we have at the surface.

    We think that within the next 20 years we are likely to see an ozone hole perhaps as big as the present one over Antarctica but over the North Pole.”

    – Joseph Farman, Brian Gardiner and Jonathan Shanklin

    That would be interesting.

    [Speculation that GW should cool the arctic and maybe produce an OH there is commonplace. I don't think its really happening yet but its not my thing -W]

  5. #5 bigcitylib

    Logically, if you can’t exclude its happening, than it can or may happen. You are quibbling.

  6. #6 Benjamin Franz

    We’ve lost more than 20% of the Arctic summer sea ice in only 3 years. There is a strong possibility that in less than ten years, for the first time in millions of years, the Arctic summer sea ice will disappear completely. Maybe even in less than 5 years (three more years like this last one would do it). The impact on the stability of the Greenland ice sheet as well as on global weather patterns would likely be nearly unimaginable.

    Those qualify as both abrupt and irreversible changes.

    [I've offered to bet people on whether next years ice will be greater or less than this years, see here. So far the response has been thin - no-one is really convinced that an irreversible decline has set in.

    Where do you get "millions of years" from? For all we know, the arctic was summer-ice-free in the Eemian. And as for the impact on the weather, there is no reason to suppose any problem -W]

    Observations have made it clear that the “worst case scenarios” of the IPCC report projections have barely qualified as “best case” of the actual events. We are 30 to 40 years ahead of projections made only a year ago already with regard to the Arctic sea ice. That means the changes are happening dozens of times faster than predicted.

    [No we aren't. We're still on the trend lines of some GCMs. THe changes are only marginally faster than the GCM average, which you shouldn't use because some of them are junk -W]

    You have a disturbing habit of downplaying both the seriousness and rapidity of AGW at every opportunity.

    [I'm quoting the IPCC, generally regarded as quite authoritative. Of course you may prefer your own interpretation -W]

  7. #7 Hank Roberts

    Ah, they wrote “abrupt or irreversible”
    – ‘and’ would have been scary, ‘or’ is reassuring.

  8. #8 Gareth

    …as for the impact on the weather, there is no reason to suppose any problem -W

    No reason? Why do you say that? A seasonally ice-free Arctic is almost certain to have a direct effect on NH weather and therefore climate – check out Jeff Masters’ blog at WeatherUnderground for some informed views on that. As the ocean cools in autumn, it loses heat to the atmosphere – and that heat has to go somewhere… At the very least, you might expect a lengthening of the NH autumn, and a shortening (or late arrival) of “traditional” winter. Quite a bit like last year, in fact…

    Stu Orto at the Weather Channel has also posted about changes in synoptics observed over the last ten years or so and their relationship to climate change. There’s also work being done at UCAR (IIRC) on the relationship between Arctic ice cover and rainfall in SW USA.

    I’ve been trying to prod some Met Soc NZ friends to look at this, but I haven’t got far yet…

    [I didn't say no changes, I said no reason to expect problems -W]

  9. #9 JesusChristHimself

    How much SLR by 2100 is sufficient to be described as being abrupt by your standard?

    One meter?

    [Not if it was uniform. "abrupt" to me means a steep change (though I suppose a change from the current 2-3 mm/yr to 10 mm/yr could be considered abrupt of itself). 5m would definitely be abrupt, but is very very unlikely -W]

  10. #10 DemocracyRules

    But in the meantime this is the same old Lasagna. Are these reports actually NEW reports, or just a recurrence of the same old report? If they’re recursions, that may enable any revisions to qualify as a type of seasonal variation.

    Printing virtually the same thing again and again, doesn’t this constitute tree abuse?

    Novelty would be an entire report detailing the substantial benefits of global warming, but I guess there are some kids who like to pull the fire alarm bell just to get attention.

    The figure with the ENTIRE PLANET in shades of red is cute, from a lasagna point of view: “Look! Look! Up in the sky… it’s on fire! The sky is burning… there, and over there too, it’s all on fire, and I can feel the heat, it’s getting hotter and hotter… ohh, my God, my God, we’re going to die, we’re all going to die…”

    [This is the synthesis report, so no, there is nothing new here -W]

  11. #11 Alexander Ač


    I don’t quite agree with this: “And as for the impact on the weather, there is no reason to suppose any problem” –

    well, then are you aware of this paper?:
    The abstract reads: “Loss of the ice cover is expected to affect the Arctic’s freshwater system and surface energy budget and could be manifested in middle latitudes as altered patterns of atmospheric circulation and precipitation.” – for instance exacerbating the drought in western US, among other effects… so?

    [Its clearly speculative. It *could* manifest as a, it could as b. It might make the drought worse, or better. As far as I can tell, at the moment the next expected gain is zero -W]

  12. #12 Adam

    “You can read the SPM and cherry-pick your favourite bit.”

    You forgot to tell us yours.

  13. #13 Alexander Ač


    but I am still not convenient with an idea that such (possibly) rapid arctic (floating) ice retreat could manifest itself as “neutral” in the net effect. Anyway, now forget about weather effects, if they are not definite.

    Surely, less (or no) floating ice at the North pole will further speed-up overall warming trend, probably also speedind-up the rate of Greenland restreat… And, we should not forget, that simply we don’t know what is the critical amount of fresh-water influx needed to shut-down THC, though IPCC clearly concludes this should not happen this century…

    [So hard to communicate... by no reason to expect weather problems I was referring to changes the sea ice might make in weather/climate elsewhere. Yes, I imagine that loss of sea ice ought to increase warming somewhat -W]

  14. #14 JesusChristHimself

    [Not if it was uniform. "abrupt" to me means a steep change (though I suppose a change from the current 2-3 mm/yr to 10 mm/yr could be considered abrupt of itself). 5m would definitely be abrupt, but is very very unlikely -W]

    It would be interesting to find out what engineers and contractors in the dike building business would consider abrupt. Somehow I think to them, given the power of the sea, one meter would add up to more than one tiger by the tail, but maybe not.

    At 5m I suspect most of them would be saying Uncle.

  15. #15 Jay Alt

    DemocracyRules – I do not agree there is nothing new in the synopsis. There are tables of less likely, but extreme events that politicians excluded from previous summaries. The problems and consequences are stated more clearly, for example -

    WG1 – http://www.ipccinfo.com/hurricanes.php

    Projections – “Contraction of the Greenland ice sheet is projected to continue to contribute to sea level rise after 2100.”

    “Both past and future anthropogenic carbon dioxide emissions will continue to contribute to warming and sea level rise for more than a millennium, due to the timescales required for removal of this gas from the atmosphere.”

    “The report gives no “best estimates” for projected sea level rise. For six emissions scenarios, it provides six projected ranges, extending from 0.18 meters (0.59 feet) to 0.59 meters (1.94 feet) between 1980-1999 and 2090-2099.”

    and then a lot of hedging under the section ‘Uncertainty’ versus –

    Synoposis Report – http://www.ipccinfo.com/wg4report.php

    Greenland Ice Sheet and Sea Level Rise
    “Contraction of the Greenland ice sheet is projected to continue to contribute to sea level rise after 2100. Current models suggest virtually complete elimination of the Greenland ice sheet and a resulting contribution to sea level rise of about 7 m if global average warming were sustained for millennia in excess of 1.9 to 4.6°C relative to pre-industrial values. The corresponding future temperatures in Greenland are comparable to those inferred for the last interglacial period 125,000 years ago, when paleoclimatic information suggests reductions of polar land ice extent and 4 to 6 m of sea level rise.”

    [This isn't new. This could have been written for the TAR (and indeed it was) -W]

  16. #16 DemocracyRules

    Well, I see that the Independent is haemorrhaging readership. It must be frustrating for those reporters. They toil so ceaselessly, generating so much imaginary information, and now to find that fewer and fewer people are reading it, why this is very sad. What, precisely, is wrong with fact abuse and truth pollution that would cause such a decline in readership?


    In the US in 2007, only 38% of those who relied on newspapers as their primary source of news said that they “get the facts straight”.

    From 1985 to 2007, opinions about the MSM have grown more negative, including declines in perceptions of their morality, protection of democracy, getting the facts straight, care in avoiding political bias, and professionalism.

    I suspect that the Independent would even have trouble with a piece featuring Economic Darwinism. They could present a detailed review describing how the financial failure of the main-stream media is linked to a publicly perceived decline in their credibility and usefulness.

    Poignantly, however, few people would read it…

  17. #17 David B. Benson

    What does “MOC” stand for?

    [Meridional Overturning Circulation -W]

  18. #18 Benjamin Franz

    W: I’ve offered to bet people on whether next years ice will be greater or less than this years, see here. So far the response has been thin – no-one is really convinced that an irreversible decline has set in.

    Ok. $100 US even money to be settled at the minimum in 2008. You have my email address.

    [OK, accepted -W]

    W:Where do you get “millions of years” from? For all we know, the arctic was summer-ice-free in the Eemian. And as for the impact on the weather, there is no reason to suppose any problem -W

    You are right on the timeline. My mistake. Amend to read “over 100,000 years”. But you have lost your mind if you honestly believe that losing the summer ice cap will not pose “any problem” for weather. It would be astounding if replacing the summer ice cap with open sea didn’t have huge impact on weather patterns. That is precisely the kind of “no big deal” statement from you that is so disturbing.

    [OK, but most of that 100 kyr was ice age so doesn't count for much :-). As for the rest... interesting; worth exploring further -W]

    W: No we aren’t. We’re still on the trend lines of some GCMs. THe changes are only marginally faster than the GCM average, which you shouldn’t use because some of them are junk -W


    [Depending on how you look (actually I withdraw "only marginally faster than GCM avg cos that isn't true, sorry). If you can access http://www.agu.org/journals/gl/gl0709/2007GL029703/2007GL029703.pdf you can see for yourself. For 1979-2006, in %/decade, the obs give -9, the GCM ensemble mean is -4. But HadGEM1 is -9, NCAR CCSM3 varies from -11 to -3 -W]


    “BOULDER–Arctic sea ice is melting at a significantly faster rate than projected by even the most advanced computer models, a new study concludes. The research, by scientists at the National Center for Atmospheric Research (NCAR) and the University of Colorado’s National Snow and Ice Data Center (NSIDC), shows that the Arctic’s ice cover is retreating more rapidly than estimated by any of the 18 computer models used by the Intergovernmental Panel on Climate Change (IPCC) in preparing its 2007 assessments.

    [Well thats not true, as their own table 1 shows, for 2 of the 3 selected time periods they use. Only for the longest - from 1950 - is the obs the largest at -8 against -5 for the model max -W]

    The study indicates that, because of the disparity between the computer models and actual observations, the shrinking of summertime ice is about 30 years ahead of the climate model projections.

    Emphasis added by me. You were saying?

    [Yes, the shrinkage is larger than the model avg shows. How do we interpret this? They consider (and don't entirely dismiss) the idea that the model avg is right, and the obs excess is natural variability. Or, the model avg is wrong -W]