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" <andrew.lock...@gmail.com> > To: "geoengineering" <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 > > 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 geoengineering@googlegroups.com To unsubscribe from this group, send email to geoengineering+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en -~----------~----~----~----~------~----~------~--~---
