Who on this list knows why the Arctic warming ~ 8,000 years ago (quite protracted and significantly warmer than today) did not lead to "runaway" warming?
Presumably something kicked in the other direction? I'm pursuing a clearer picture of lessons from the Holocene and the Eemian (the previous interglacial) related to feedbacks and whether there are, or are not, one-way doors in the climate system. Leads eagerly pursued. .. Andy At 5:29 PM +0530 2/2/09, Govindasamy bala wrote: >Runaway feedback means running its course completely. It is feedback specific. > >A good example is the presumed water vapor feedback on Venus. >Apparently, earth and venus started with similar amount of h2o. >Because Venus started with much higher surface temperature, the >evolution of temperature and water vapor never intercepted the phase >line of vapor and liquid. The climate warmed until all the water got >evaporated. Basically, there was no sink for vapor which >precipitation. On earth, this is not going to happen because we got >the precipitation sink on earth...how lucky we are. > >But I guess we do have runaway ice-albedo feedback on earth. we >could get ice-free planet or snowball earth........ > >Cheers. >Bala > >On Mon, Feb 2, 2009 at 5:03 PM, Eugene I. Gordon ><<mailto:euggor...@comcast.net>euggor...@comcast.net> wrote: > > >I guess it is not going to end. > >A runaway train meets only #2 and even that has to be qualified because the >train eventually runs out of (fossil?) fuel or track. Certainly climate has >run away a half dozen times in 540 million years but always hits a limit >which seems to be 24C except when an asteroid hits. It eventually turns >around after remaining at the limit temperature for many millions of years. >We have been in a runaway mode for the last 18,000 years but with some >superimposed small wiggles in temperature. Without geoengineering the >temperature will certainly get to the 24 C limit. > >I think runaway is appropriate for the current situation even if there may >be better suited terms. > > >-----Original Message----- >From: <mailto:geoengineering@googlegroups.com>geoengineering@googlegroups.com > >[mailto:<mailto:geoengineering@googlegroups.com>geoengineer...@googlegroups.com] > >On Behalf Of John Nissen >Sent: Monday, February 02, 2009 6:08 AM >To: Tom Wigley; Andrew Lockley >Cc: geoengineering; Prof John Shepherd; Tim Lenton; David Lawrence >Subject: [geo] Re: runaway climate change > > > >Dear Tom, > >The concept of "runaway" has certain connotations: > >1. Significant in resultant effect >2. Uncontrollable >3. Exponential initial behaviour - characteristised by acceleration of >process 4. No obvious limit 5. Irreversible 6. Rapid. > >These can all be applied to climate change: > >1. "Significant" could be over 5 degrees global warming, sufficient for a >mass extinction event. Or it could be applied to several metres of sea >level rise. >2. "Uncontrollable" could be where anthropogenic greenhouse gas emissions >reduction would not have a significant effect on the rate of climate change. >3. Exponential behaviour could be caused by a "tipping" of some part of the >climate system, such as Arctic sea ice or methane release, where there is >strong positive feedback. >4. There would be no obvious final equilibrium temperature - mainly because >of the difficulty of modelling positive feedback and its behaviour over >time. >5. It would be extremely difficult or impossible to reverse processes such >as methane release or Greenland ice sheet disintegration, although it is >conceivable to halt these processes or even reverse their effects >(presumably through geoengineering). >6. "Rapid" could be anything from one season to 3000 years, on a geological >timescale. > >Therefore I think that "runaway" captures the semantics that we require for >the climate change that would result from, for example, a massive methane >release, triggered by Arctic sea ice disappearance. Can you think of a >better word to capture the six characteristics above, especially as >applicable to climate change? > >Cheers, > >John > > > >----- Original Message ----- >From: "Tom Wigley" <<mailto:wig...@ucar.edu>wig...@ucar.edu> >To: "Andrew Lockley" ><<mailto:andrew.lock...@gmail.com>andrew.lock...@gmail.com> >Cc: <<mailto:j...@cloudworld.co.uk>j...@cloudworld.co.uk>; "geoengineering" ><<mailto:geoengineering@googlegroups.com>geoengineering@googlegroups.com>; >"Prof John Shepherd" ><<mailto:j...@noc.soton.ac.uk>j...@noc.soton.ac.uk>; "Tim Lenton" ><<mailto:t.len...@uea.ac.uk>t.len...@uea.ac.uk>; "David Lawrence" ><<mailto:dlaw...@ucar.edu>dlaw...@ucar.edu> >Sent: Monday, February 02, 2009 3:43 AM >Subject: Re: [geo] Re: runaway climate change > > >> Andrew, >> >> Poor analogy. running does not equal running away. >> >> More importantly, just because a term has been misused in the >> past does not mean we should perpetuate its misuse (or use). >> If the word is to be used at all (and, as a practicing scientist, >> I never have or will), one should start off by saying that the >> word runaway is open to misinterpretation, that it does not >> mean running off to infinity, and that it's real meaning is ... >> etc. etc. Then talk about irreversible changes (with the caveat >> that even these are probably not irreversible), positive >> feedbacks (which also have limits), etc. >> >> Tom. >> >> +++++++++++++++++++++++==== >> >> Andrew Lockley wrote: >>> For better or worse, the term is now in general use in scientific, >>> industrial, environmental and general media. (See >>> >>><http://en.wikipedia.org/wiki/Runaway_climate_change>http://en.wikipedia.org/wiki/Runaway_climate_change >>> >>>for refs.) >>> >>> I don't agree with Tom about 'to infinity and beyond'. I run as a >>> hobby, and I've never run to infinity (or beyond). I think most >>> people realise that runaway doesn't mean run-for-ever. >>> >>> However, a general definition would be very useful. >>> >>> A >>> >>> 2009/2/2 <<mailto:wig...@ucar.edu>wig...@ucar.edu>: >>>> Dear All, >>>> >>>> I've said this before, but here goes again. >>>> >>>> If one sticks to dictionary definitions of words (which I >>>> think is wise) then there is no such thing as "runaway" >>>> climate change. Strictly, using the words of Buzz Lightyear, >>>> "runaway" must mean "to infinity and beyond". >>>> >>>> Further, the word "runaway" is loaded and should be eschewed >>>> in the climate context. >>>> >>>> The confusion here is that what some people are calling >>>> "runaway" climate change is really better referred to as >>>> "irreversible" climate change. For instance, the sudden release >>>> of a large amount of CH4 would possibly cause large warming >>>> that would put the globe in a new state that was much warmer >>>> than present. But the climate (or global-mean temperature) would >>>> *not* runaway -- it would eventually stabilize. Even this change >>>> would not strictly be irreversible, as the excess CH4 would >>>> slowly be oxidized (more slowly than today because of the well >>>> known positive feedback of CH4 on its own lifetime due to OH loss), >>>> but a lot of the excess CH4 would slowly disappear and be replaced >>>> by CO2 that has less forcing. This CO2 would, of course, stay >>>> around for a long time. >>>> >>>> If anyone is interested, this case can easily be run with MAGICC, >>>> but some minor tweaks are needed to get the CH4 to CO2 flux right. >>>> Conceptually trivial. >>>> >>>> So, please, please try not to cry wolf with these loaded and sadly >>>> oft-misused words. >>>> >>>> Tom. >>>> >>>> ++++++++++++++++++++++++++++ >>>> >>>>> >>>>> Andrew, >>>>> >>>>> 1. I think the concept of runaway climate change is kosher. See this >>>>> quote >>>>> from >>>>> >>>>><http://www.meridian.org.uk/_PDFs/FeedbackDynamics.pdf>http://www.meridian.org.uk/_PDFs/FeedbackDynamics.pdf >>>>> >>>>> "The possibility of a tipping point in the earth system as a whole >>>>> which >>>>> prevents the recovery of stable equilibrium and leads to a process of >>>>> runaway climate change, is now the critical research agenday, requiring > >>>> the >>>>> concerntration of global resources in a "Manhattan Project" style >>>>> engagement. All other work on impact assessment, mitigation and >>>>> adaptration >>>>> depends on the outcome of thie overarching issue" >>>>> >>>>> I would prefer to have "runaway global warming", because that's what we >>>>> are >>>>> really talking about, but "climate change" is almost interchangeable >>>>> with >>>>> "global warming" these days. >>>>> >>>>> 2. The domino effect is mentioned here: >>>>> >>>>> <http://researchpages.net/ESMG/people/tim-lenton/tipping-points/>http://researchpages.net/ESMG/people/tim-lenton/tipping-points/ >>>>> >>>>> The release of methane is likely to be triggered by the loss of Arctic >>>>> sea >>>>> ice, according to David Lawrence: >>>>> >>>>><http://www.ucar.edu/news/releases/2008/permafrost.jsp>http://www.ucar.edu/news/releases/2008/permafrost.jsp >>>>> >>>>> 3. I believe it is generally accepted that the Arctic sea ice albedo >>>>> effect >>>>> contributes to the accelerated warming trend in the Arctic region. It >>>>> is >>>>> also accepted that this effect presents a strong positive feedback on >>>>> the >>>>> local warming, but currently presents only a weak positive feedback on >>>>> global warming. Thus if the local warming can be halted, and methane >>>>> release domino effect thereby avoided, then we can avoid passing a >>>>> point >>>>> of >>>>> no return, or going "over the waterfall" as you put it. >>>>> >>>>> I'd be interested to know if Prof John Shepherd agrees with this >>>>> assessment. >>>>> >>>>> 4. Additional point - only albedo (shortwave radiation) geoengineering >>>>> has >>>>> any chance to halt the local warming in the Arctic. >>>>> >>>>> Again I'd be interested to know whether Prof Shepherd agrees with this. >>>>> >>>>> Cheers, >>>>> >>>>> John >>>>> >>>>> >>>>> ----- Original Message ----- >>>>> From: "Andrew Lockley" >>>>><<mailto:andrew.lock...@gmail.com>andrew.lock...@gmail.com> >>>>> To: "geoengineering" >>>>><<mailto:geoengineering@googlegroups.com>geoengineering@googlegroups.com> >>>>> Sent: Sunday, February 01, 2009 12:33 PM >>>>> Subject: [geo] runaway climate change >>>>> >>>>> >>>>> I'm working on >>>>><http://en.wikipedia.org/wiki/Runaway_climate_change>http://en.wikipedia.org/wiki/Runaway_climate_change >>>>> >>>>> and there are a few crucial questions I could do with help on: >>>>> >>>>> 1) Is the term 'Runaway climate change' seen as kosher, or is it >>>>> purely a pop-science concept? >>>>> 2) How widespread is support for the idea of an ice-albedo followed by >>>>> a clathrate/permafrost domino effect? Is it speculative or accepted? >>>>> 3) Is there consensus on 2) above as regards timing? All the sound >>>>> evidence I've read says we've already fallen over the waterfall. Do >>>>> others agree? >>>>> >>>>> If you have any general thoughts on the matter, or notable people and >>>>> sources you'd care to inform me of, then please email back >>>>> [snip] >>>>> >>>>> >>>>> >>>> >>>> >> >> >> > > > > > > > >-- >Best wishes, > >------------------------------------------------------------------- >Dr. G. Bala >Associate Professor >Center for Atmospheric and Oceanic Sciences >Indian Institute of Science >Bangalore - 560 012 >India > >Tel: +91 80 2293 2698 > +91 80 2293 2505 x206 > +91 9741991621 (cell) >Fax: +91 80 2360 0865 >Email: <mailto:gb...@caos.iisc.ernet.in>gb...@caos.iisc.ernet.in > <http://bala.gov>bala.gov@<http://gmail.com>gmail.com >Web:<http://caos.iisc.ernet.in/faculty/gbala/gbala.html>http://caos.iisc.ernet.in/faculty/gbala/gbala.html >------------------------------------------------------------------- > > -- Andrew C. Revkin The New York Times / Environment 620 Eighth Ave., NY, NY 10018 Tel: 212-556-7326 Mob: 914-441-5556 Fax: 509-357-0965 http://www.nytimes.com/revkin --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "geoengineering" group. 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