The term "runaway" has an accepted meaning in the context of "thermal runaway", and is characterised by positive feedback and resulting acceleration in temperature change. So the temperature rises more than linearly, and may even rise exponentially or "explosively": http://en.wikipedia.org/wiki/Thermal_runaway Eventually the feedback peters out, and the temperature change becomes linear again.
This process is happening with the Arctic sea ice. At present the albedo feedback effect is causing an acceleration in temperature change in the polar region - but this positive feedback will eventually peter out, when all the ice and snow in the region has melted, including the Greenland ice sheet! So we are facing thermal runaway on a regional scale, affecting local climate and ecosystem. This will have a domino effect on methane release. As the Arctic region warms, methane will invitably be released in larger and larger quantities. The speed of methane release depends critically on the temperature above the frozen structure holding the methane. For permafrost on land, if the average surface temperature is maintained above freezing, the permafrost will inevitably melt. This is what is happening over vast areas of Canada and Siberia, as the isotherms (lines of equal temperature on a map) move northwards. The methane itself provides feedback equally to both regional and global warming, through its greenhouse effect. The regional warming will increase the rate of methane release. Thus there could be thermal runaway on a global scale and "we are toast", as Hansen puts it. We have to find a way to quickly halt the Arctic regional warming. I maintain that the key to this is to halt and partially reverse the retreat of the Arctic sea ice, by cooling the region. And I maintain that the key to cooling is use of solar radiation management (SRM) techniques - a combination of stratospheric aerosols and marine cloud brightening. If we do not act quickly with our SRM geoengineering, then thermal runaway from methane (and also disasterous sea level rise) could become inevitable. Cheers from Chiswick, John P.S. Note that geoengineering to reduce atmospheric CO2. ----- Original Message ----- From: "Andrew Lockley" <andrew.lock...@gmail.com> To: "Geoengineering FIPC" <geoengineering@googlegroups.com> Sent: Thursday, February 05, 2009 2:28 AM Subject: [geo] runaway arguments ripped to bits > > After getting thoroughly shouted at, I realised I needed to improve my > 'runaway' arguments. > > My current skeleton is below. However, it's currently missing a few > crucial bones which now need replacing. I need citations for the > following: > > 1) A clathrate gun effect that shows rapid release? Buffett and > Archer, and Archer alone, show a slow release, although from a large > reservoir. > 2) A calculation of the eventual warming that may result from methane > release from permafrost/clathrates. > 3) A study showing the impacts of such a level of warming on human > civilisation/survival. > 4) What happens to methane sinks under conditions of bulk outgassing? > Do they fail and massively increase the global warming potential of > methane? > > We've discussed all these issues before, but I think it's now time to > get any available research on the issue into the open. Is there > REALLY a big and immediate risk from the clathrate gun/permafrost? > > A > > http://en.wikipedia.org/wiki/Effects_of_global_warming#Abrupt_climate_change > > The scientific consensus in the [[IPCC Fourth Assessment Report]] is > that "Anthropogenic warming could lead to some effects that are abrupt > or irreversible, depending upon the rate and magnitude of the climate > change." > > The phenomenon of [[Arctic shrinkage]] is leading some scientists to > fear that a runaway climate change event may be > imminent<ref>http://www.guardian.co.uk/environment/2006/oct/18/bookextracts.books</ref>, > and may even have > started<ref>http://www.terranature.org/environmentalCrisis.htm</ref>. > There is an [[albedo]] effect, as white ice is replaced by dark ocean. > Rapid [[Arctic shrinkage]] is occurring, with 2007 being the lowest > ever recorded area and 2008 being possibly the lowest ever recorded > volume.<ref>http://nsidc.org/news/press/20081002_seaice_pressrelease.html</ref> > This will induce or accelerate other [[positive feedback]] mechanisms, > such as [[Arctic methane release]] from melting [[permafrost]] and > [[clathrates]]. Lawrence et al(2008) suggests that a rapid melting of > the sea ice may up a feedback loop that rapidly melts arctic > permafrost.<ref>http://www.ucar.edu/news/releases/2008/permafrost.jsp</ref><ref>{{Citation > | year=2008 | title=Accelerated Arctic land warming and permafrost > degradation during rapid sea ice loss | first=David M. | last=Lawrence > | first2=Andrew G. | last2=Slater | first3=Robert A. | last3=Tomas | > first4=Marika M. | last4=Holland | first5=Clara | last5=Deser | > journal=[[Geophysical Research Letters]] | volume=35 | issue=11 | > doi=10.1029/2008GL033985 | > url=http://www.cgd.ucar.edu/ccr/dlawren/publications/lawrence.grl.submit.2008.pdf}}</ref> > > Estimates of the size of the total carbon reservoir in Arctic > [[permafrost]] and [[clathrates]] vary widely. It is suggested that > at least 900 gigatonnes of carbon in permafrost exists > worldwide.<ref>http://www.terranature.org/methaneSiberia.htm</ref>{{fact}}. > Further, there are believed to be around and another 400 gigatonnes > of carbon in methane clathrates in permafrost regions > alone.<ref>http://www.springerlink.com/content/r4w867922g607w2j/</ref>. > Should this estimate of volume be correct or at least too low, and if > clathrates are omitted from the analysis completely, then 900 > gigatonnes of carbon may potentially be released as methane as a > result of human activity. [[Methane]] is a potent [[greenhouse gas]] > with a higher [[global warming potential]] than [[CO2]]. A release on > this scale will create [[catastrophic climate change]]. > > > > --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
