As I understand the science, I think it would be premature to precisely estimate the gain factor without stating error bars. Can we really be confident that we've got it nailed to the 25% error margin we need, when we can't even agree to within a 50-year window when the Arctic will melt?
I do actually think this discussion is very useful here, as this debate pretty much underpins one of the really fundamental arguments behind geoeng. As regards wiki work, I am trying to do the best i can with a term in general use. It is very controversial. I hope you can have a look at the article http://en.wikipedia.org/wiki/Runaway_climate_change it's discussion page http://en.wikipedia.org/wiki/Talk:Runaway_climate_change and discussion about its potential deletion http://en.wikipedia.org/wiki/Wikipedia:Articles_for_deletion/Runaway_climate_change A 2009/2/2 John Nissen <[email protected]>: > > 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" <[email protected]> > To: "Andrew Lockley" <[email protected]> > Cc: <[email protected]>; "geoengineering" > <[email protected]>; "Prof John Shepherd" > <[email protected]>; "Tim Lenton" <[email protected]>; "David Lawrence" > <[email protected]> > 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 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 <[email protected]>: >>>> >>>> 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 >>>>> >>>>> "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/ >>>>> >>>>> 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 >>>>> >>>>> 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" <[email protected]> >>>>> To: "geoengineering" <[email protected]> >>>>> 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 >>>>> >>>>> 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] >>>>> >>>>> >>>>> >>>>> >>>> >> >> >> > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en -~----------~----~----~----~------~----~------~--~---
