Few thoughts about different types of runaway climate change 1) Positive feebacks and anthropogenic releases in combinations move the climate system to a state of increasing independency from its initial anthropogenic GHG influence. Human inability, where a true inability to effect GHG reduction cuts exist is accounted as a part of the positive forcing, 'background forcing'. Avoidable emissions are treated separately, one could call this as a sub-natural runaway warming where combination tips system runaway. Positive feedbacks build up independently of any anthropogenic additional releases of CO2 and CH4 cause the GHG forcing grow at moderate rate. >> Can on its initial onset be stopped or slowed by accommodation by reducing man-made emissions. The feedback amount of CO2 released is < less or = than 1 anthropogenic GHG release. Emission cuts with moderate alternative influencing can bring system under control with some required intervention. 2) Positive feedbacks build up independently of any anthropogenic additional releases of CO2 and CH4 causing the GHG forcing at medium rate. >> Both forestation, sun shades and other agressive intervention may be required to subdue feedbacks. Thermal inertia of earth system buys time when emissions at = 1 anthropogenic GHG release. Chance events like solar out put, volcanic activity and weather events become increasingly important factors for the successful management of situation. 3) Positive feedbacks build up independently of any anthropogenic additional releases of CO2 and CH4 causing the GHG forcing at high rate. >> Only most agressive intervention may reduce rate of escalation if the positive feedback emission is few times anthropogenic GHG release, but successfull means to rain back further positive feedbacks is greatly reduced and increasingly unlikely by geoengineering and other means. CH4 component in positive feedback may be somewhat mitigable due to shorter life cycle by geoengineering therapies like sulphur oxides. 4) Positive feedbacks build up independently of any anthropogenic additional releases of CO2 and CH4 causing the GHG forcing at extreme rate. >> Only rate of escalation can be somewhat plugged without any possibility to get proper lasting results within given time frame, i.e. to build solar shades in time in space to block sunlight etc. I would suggest that we should call this as Extinction Event, or perhaps, Terminal Climate Change of my favourite 'popcorn evolution' (to explain why SETI do not return signal from other civilisations who have already destroyed themselves). > Date: Mon, 2 Feb 2009 09:08:11 -0800> Subject: [geo] Re: runaway climate > change> From: [email protected]> To: > [email protected]> > > Dear Group,> > To me a runaway > greenhouse means the negative feedbacks have been> overwhelmed by > accelerating positive forcing. In such a case only an> ice age could reverse > the runaway effect, a few other checks could> contribute (CLAW hypothesis). > If an ice age cannot cool the planet> and stop the positive feedbacks, > temperature will increase until we> reach a new steady state. I don't know > what that would be. Some have> said that we could end up as the next Venus.> > > Sincerley,> > Oliver Wingenter> > On Feb 2, 4:59 am, Govindasamy bala > <[email protected]> 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 <[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_changefor 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 onhttp://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> >> > ...> >> > > read more ยป> _________________________________________________________________
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