Page # 71 of the book "Global warming: Understanding the forecast" by David Archer has a nice description on runaway feedback. BTW, I guess there is no such thing as runaway climate change.... B
On Mon, Feb 2, 2009 at 5:55 PM, Andrew Lockley <[email protected]>wrote: > > I have been unable to find any citations in 'hard' climate science > literature. Is the term therefore ONLY a pop-science concept? > > If anyone has any such citations, please can they send them to me? > > A > > 2009/2/2 David Schnare <[email protected]>: > > The concept, as applied to climate change, was introduced to discuss loss > of > > ice shelves, an "irreversible" event over the short run, and one with > large > > consequences. Then, the concept was expanded to the speed of the event, > > also as applied to the ice shelves. Then it was expanded to the "fat > tail" > > possibility of very high temperatures. > > > > In each case, the presumption (presumption, not reality mind you) was > that > > the event was unstoppable once started, much like an explosion. The > > inability to "quench" an event should not be confused with the ability to > > restore (more or less) the initial conditions, or otherwise reach a (new > or > > modified) equilibrium. > > > > "Runaway" is a loaded term. We've had a dust up over use of such terms > in > > the recent past. As far as I can tell, at this point, environmental > > activists are allowed to use them, government employees are not, > scientists > > should not, and wiki authors - god knows! > > > > Cheers, > > d. > > > > On Mon, Feb 2, 2009 at 6:33 AM, Eugene I. Gordon <[email protected]> > > 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: [email protected] > >> [mailto:[email protected]] 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" <[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] > >> >>>> > >> >>>> > >> >>>> >>>> > >> >>> > >> > > >> > > >> > > >> > >> > >> > >> > >> >> > > > > > > > > -- > > David W. Schnare > > Center for Environmental Stewardship > > > > > > -- 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: [email protected] [email protected] Web:http://caos.iisc.ernet.in/faculty/gbala/gbala.html ------------------------------------------------------------------- --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
