Talk:Runaway climate change

Merging Articles
This article could be merged with Tipping point (climatology) and Abrupt climate change? They appear to be closely related!

Id447 (talk) 22:16, 19 May 2010 (UTC)


 * I almost agree 100%, and as no one has objected to your suggestion in over a year, I'm going to start working on that by copying sections that follow "definition", on an as-needed basis to the abrubt climate change article. For the time being I'll leave the copied sections in this article and I'll report an update here with my progress in a few days.  NewsAndEventsGuy (talk) 18:46, 27 June 2011 (UTC)


 * OOPS scratch that. I just remembered the official merge process so I'll follow that course instead. NewsAndEventsGuy (talk) 19:05, 27 June 2011 (UTC)

Tags
Anyone still want the tags? William M. Connolley (talk) 22:35, 2 September 2010 (UTC)

The verifiable sources state it is a theory, why is that a problem?
Currently the very first source given for the first line of the definition section states "Runaway climate change is a theory of how things might go badly wrong for the planet if a relatively small warming of the earth upsets the normal checks and balances that keep the climate in equilibrium." it doesn't matter what we think it is or isn't - for example, it may well be better desribed as a model (and maybe that is why VSmith thinks it's "not really a theory") but that is not what the verifiable sources say - the first source used states in the first six words of the work that "runaway climate change is a theory" [emphasis added]. What the heck is the problem with using the description as given in the verifiable source? The correction to "theory" has been removed twice now with no other reasons that "cpy" and "not really a theory" when the source says otherwise.--163.1.147.64 (talk) 18:27, 12 December 2010 (UTC)

Remove Confusing Notice
Can we remove the 2009 (4 years!) confusing notice of this article? The article could be improved but i don't see how it would be confusing. Prokaryotes (talk) 04:41, 18 September 2013 (UTC)


 * Boris added it during the ALJ wars . Now he's gone, we could render the article sane then remove the notice, perhaps? William M. Connolley (talk) 11:20, 18 September 2013 (UTC)
 * Could someone point out particular parts which require the most attention? I think the main scope of this article should be the physical process (thresholds, feedbacks and tipping points), our understanding and projected impacts based on past events on Earth and Venus. It would be also good to make a distinction between short/mid/long term developments and considerable "end states" like that on Venus. See parts of the article Atmosphere of Venus is also relevant here. Prokaryotes (talk) 17:05, 18 September 2013 (UTC)
 * William, i see you editing currently. Please change the entry part again - The media is using this term because it is used in the literature, over decades. The term is not clearly defined, however it is not "rarely" used. It is especially used when studying the Venus atmosphere. Also a section called "Examples" could include Venus and Jenkinson. Consider it. Prokaryotes (talk) 18:57, 18 September 2013 (UTC)
 * Ok, maybe make more clear the difference to Runaway greenhouse effect. Prokaryotes (talk) 19:06, 18 September 2013 (UTC)

Runaway Greenhouse
Our climate simulations, using a simplified three-dimensional climate model to solve the fundamental equations for conservation of water, atmospheric mass, energy, momentum and the ideal gas law, but stripped to basic radiative, convective and dynamical processes, finds upturns in climate sensitivity at the same forcings as found with a more complex global climate model [66]. At forcings beyond these points the complex model ‘crashed’, as have other climate models (discussed by Lunt et al. [83]). The upturn at the 10–20 W m−2 negative forcing has a simple physical explanation: it is the snowball Earth instability. Model crashes for large positive forcings are sometimes described as a runaway greenhouse, but they probably are caused by one of the many parametrizations in complex global models going outside its range of validity, not by a runaway greenhouse effect.

The runaway greenhouse effect has several meanings ranging from, at the low end, global warming sufficient to induce out-of-control amplifying feedbacks, such as ice sheet disintegration and melting of methane hydrates, to, at the high end, a Venus-like hothouse with crustal carbon baked into the atmosphere and a surface temperature of several hundred degrees, a climate state from which there is no escape. Between these extremes is the moist greenhouse, which occurs if the climate forcing is large enough to make H2O a major atmospheric constituent [106]. In principle, an extreme moist greenhouse might cause an instability with water vapour preventing radiation to space of all absorbed solar energy, resulting in very high surface temperature and evaporation of the ocean [105]. However, the availability of non-radiative means for vertical transport of energy, including small-scale convection and large-scale atmospheric motions, must be accounted for, as is done in our atmospheric general circulation model. Our simulations indicate that no plausible human-made GHG forcing can cause an instability and runaway greenhouse effect as defined by Ingersoll [105], in agreement with the theoretical analyses of Goldblatt & Watson [128].

On the other hand, conceivable levels of human-made climate forcing could yield the low-end runaway greenhouse. A forcing of 12–16 W m−2, which would require CO2 to increase by a factor of 8–16 times, if the forcing were due only to CO2 change, would raise the global mean temperature by 16–24°C with much larger polar warming. Surely that would melt all the ice on the planet, and probably thaw methane hydrates and scorch carbon from global peat deposits and tropical forests. This forcing would not produce the extreme Venus-like baked-crust greenhouse state, which cannot be reached until the ocean is lost to space. A warming of 16–24°C produces a moderately moist greenhouse, with water vapour increasing to about 1% of the atmosphere's mass, thus increasing the rate of hydrogen escape to space. However, if the forcing is by fossil fuel CO2, the weathering process would remove the excess atmospheric CO2 on a time scale of 104–105 years, well before the ocean is significantly depleted. Baked-crust hothouse conditions on the Earth require a large long-term forcing that is unlikely to occur until the sun brightens by a few tens of per cent, which will take a few billion years http://m.rsta.royalsocietypublishing.org/content/371/2001/20120294.full


 * I try to extract a meaningful part and update this and the other page. Is CC-BY Prokaryotes (talk) 00:39, 19 September 2013 (UTC)