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 or just come and edit ( http://en.wikipedia.org/w/index.php?title=Runaway_climate_change&action=edit ) or discuss the article ( http://en.wikipedia.org/wiki/Talk:Runaway_climate_change ) article follows: ----------------------------- Runaway climate change >From Wikipedia, the free encyclopedia Main articles: Greenhouse effect and Global Warming See also: Abrupt climate change for a discussion of paleoclimatology events Runaway climate change describes an event where climate change passes a tipping point and undergoes self-sustaining acceleration due to positive feedback effects.[citation needed] Scientists, including James Hansen believe that Arctic shrinkage caused by global warming has already initiated runaway climate change due to ice-albedo feedback. Lawrence then suggests a further feedback mechanism from consequential methane release from permafrost and clathrates.[1] The risk of this effect has led many scientists to suggest geoengineering. Once started, runaway climate change will continue until the feedback loop is interrupted. For example, an ice-albedo feedback can only continue until all the ice has melted. Once a period of runaway climate change has started, the only way to stop it is by geoengineering to artificially break the feedback loop. An example of such a technique would be by using stratospheric sulfur aerosols to alter reduce insolation. Although the phenomenon itself is based on sound science, the expression runaway climate change is more commonly used in mass media than in scientific literature. This article may contain original research or unverified claims. Please improve the article by adding references. See the talk page for details. (January 2009) When a change in global temperature causes something to happen which itself then acts to change global temperatue, there exists a climate feedback mechanism. If the effect acts in the same direction on temperature it is a positive feedback; and if in the opposite direction it is a negative feedback. Feedback effects can be on the same cause as the forcing, via another greenhouse gas, or on other effects such as change in ice cover affecting the planet's albedo. Some commentators[who?] use the expression runaway climate change solely to describe a situation where the climate deviates catastrophically and permanently from the original state - as happened on Venus, rendering the planet radically different from Earth despite its similar origins.[dubious – discuss] Most runaway climate change scenarios expected as a result of global warming involve changes to the methane deposits in permafrost and clathrates[citation needed]. Current global climate models do not generally include sophisticated modelling of methane deposits, making them unable to accurately predict climate tipping points.[citation needed] The weakness of the modelling used is believed to be factor in the acceleration of Arctic shrinkage above IPCC estimates. Contents [hide] 1 Mechanisms 2 Current risk 3 Terrestrial Precedents 4 Extra-terrestrial Precedents 5 References [edit]Mechanisms Many feedback processes exist in climate systems, which act either to stabilise or destabilise the system according to whether they are negative or positive feedbacks. A positive feedback is one which tends to amplify the effect of any change to the climate. In the example of global warming, a positive feedback mechanism is a process caused by global warming (such as the loss of sea ice) which then causes further warming. Examples of positive feedback mechanisms for global warming include: Loss of sea ice, exposing darker ocean and loss of glaciers and ice caps, exposing darker rock beneath. The clathrate gun effect, which describes the release of methane from ocean stores of methane hydrate (AKA clathrate). Release of methane from permafrost The above positive feedbacks have always existed; yet climate over the last ten thousand years of the Holocene has been quite stable; there has been no runaway effect. With radiation from the Earth increasing in proportion to the fourth power of temperature, in accordance with the Stefan-Boltzmann law, the feedback effect has to be very strong to cause a runaway effect. An example of a positive feedback mechanism which does not cause runaway climate change is the evaporation of water. An increase in temperature from greenhouse gases may lead to increased water vapour in the atmosphere. Water vapour is a greenhouse gas, which cause further warming is a positive feedback. However, this cannot be a runaway effect or the runaway effect would have occurred long ago. Positive feedback effects are common and can always exist while runaway effects are much rarer and cannot be operating at all times. If the effects from the second iteration of the loop of effects is larger than the effects of the first iteration of the loop this will lead to a self perpetuating effect. If this occurs and the feedback only ends after producing a major temperature increase, it is called a runaway greenhouse effect or climate tipping point. It has been speculated that a runaway feedback could also occur in the opposite direction leading to an ice age, based on the shutdown of thermohaline circulation, as depicted in the film The Day After Tomorrow. Runaway feedbacks are bound to stop eventually, since infinite temperatures are not observed. They are stopped by factors like a reducing supply of a greenhouse gas or a phase change of the gas, or ice cover reducing towards zero or increasing toward a large size that is difficult to increase. [edit]Current risk The phenomenon of Arctic shrinkage is leading some scientists to fear that a runaway climate change event may be imminent[2], and may even have started[3]. Rapid Arctic shrinkage is occurring, with 2007 being the lowest ever recorded area and 2008 being possibly the lowest ever recorded volume.[4] This will induce positive feedback mechanisms: Albedo effect, as white ice is replaced by dark ocean, possibly as early as 2013[5] James Hansen argues that geoengineering is the only way to save the Arctic sea ice , as we are likely already to have passed the tipping point and it is too late for carbon emissions reduction to work.[6] 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.[7][8] It takes about 100 years for permafrost to be fully released methane[9], and methane clathrates release probably much faster than that.[citation needed] Estimates of the size of the total carbon reservoir in Arctic permafrost and clathrates vary widely. It is suggested that is at least 900 gigatonnes of carbon in permafrost worldwide.[10]. Further, there are believed to be around and another 400 gigatonnes of carbon in methane clathrates in permafrost regions alone.[11]. However, Buffett and Archer predict a much higher release of between 2,000 and 4,000 gigatonnes as a result of expected human-induced warming, as they include some deep-ocean clathrate stores in the expected release.[12] Should the more conservative estimate be correct or at least too low, then 1300 gigatonnes of carbon may potentially be released as methane from permafrost and clathrates as a result of human activity. As methane is a potent greenhouse gas, this is equivalent to a release of carbon dioxide very roughly 50 times the total emitted by humans since the Industrial Revolution. A release on this scale, or even a fraction of it, will create catastrophic climate change and is likely to lead to a complete collapse of human civilisation.[13] [edit]Terrestrial Precedents Main articles: Abrupt climate change and Paleoclimatology Geological records indicate that runaway climate change is not unprecedented. According to the clathrate gun hypothesis a runaway greenhouse effect could be caused by liberation of methane gas from hydrates by global warming if there are sufficient hydrates close to unstable conditions. It has been speculated that the Permian-Triassic extinction event[14] and the Paleocene-Eocene Thermal Maximum[citation needed] were caused by such a runaway effect. It is also thought that large quantities of methane could be released from permafrost in the Siberian tundra as it begins to thaw. Methane is 21 times more potent a greenhouse gas than carbon dioxide.[15] (N.B. its potency is higher over shorter timescales, as its lifespan in the atmosphere is limited. See Global Warming Potential) [edit]Extra-terrestrial Precedents This article's factual accuracy is disputed. Please see the relevant discussion on the talk page. (January 2009) A runaway greenhouse effect involving CO2 and water vapor may have occurred on Venus.[16] In this scenario, early Venus may have had a global ocean. As the brightness of the early sun increased, the amount of water vapor in the atmosphere increased, increasing the temperature and consequently increasing the evaporation of the ocean, leading eventually to the situation in which the oceans boiled, and all of the water vapor entered the atmosphere. On Venus today there is little water vapor in the atmosphere. If water vapor did contribute to the warmth of Venus at one time, this water is thought to have escaped to space. Venus is sufficiently strongly heated by the Sun that water vapor can rise much higher in the atmosphere and be split into hydrogen and oxygen by ultraviolet light. The hydrogen can then escape from the atmosphere and the oxygen recombines. Carbon dioxide, the dominant greenhouse gas in the current Venusian atmosphere, likely owes its larger concentration to the weakness of carbon recycling as compared to Earth, where the carbon dioxide emitted from volcanoes is efficiently subducted into the Earth by plate tectonics on geologic time scales.[17][18] [edit]References ^ Lawrence, David M.; Slater, Andrew G.; Tomas, Robert A.; Holland, Marika M.; Deser, Clara (2008), "Accelerated Arctic land warming and permafrost degradation during rapid sea ice loss", Geophysical Research Letters 35 (11), doi:10.1029/2008GL033985 ^ http://www.guardian.co.uk/environment/2006/oct/18/bookextracts.books ^ http://www.terranature.org/environmentalCrisis.htm ^ http://www.nsidc.org/news/press/20070430_StroeveGRL.html ^ http://news.bbc.co.uk/1/hi/sci/tech/7139797.stm ^ http://www.independent.co.uk/environment/climate-change/the-earth-today-stands-in-imminent-peril-453708.html ^ http://www.ucar.edu/news/releases/2008/permafrost.jsp ^ Lawrence, David M.; Slater, Andrew G.; Tomas, Robert A.; Holland, Marika M.; Deser, Clara (2008), "Accelerated Arctic land warming and permafrost degradation during rapid sea ice loss", Geophysical Research Letters 35 (11), doi:10.1029/2008GL033985 ^ http://www.sciencemag.org/cgi/content/summary/312/5780/1612 ^ http://www.terranature.org/methaneSiberia.htm ^ http://www.springerlink.com/content/r4w867922g607w2j/ ^ http://adsabs.harvard.edu/abs/2005AGUSM.U33A..05B ^ http://www.ecoearth.info/shared/reader/welcome.aspx?linkid=51491 ^ How to kill (almost) all life: the end-Permian extinction event, Michael J. Benton and Richard J. Twitchett, Department of Earth Sciences University of Bristol UK, TRENDS in Ecology and Evolution Vol.18 No.7 July 2003, doi:10.1016/S0169-5347(03)00093-4 (full reprintPDF (506 KiB)) ^ Climate change: 'One degree and we're done for' - earth - September 27, 2006 - New Scientist Environment ^ Rasool, S.I.; C. de Bergh (1970). "The Runaway Greenhouse Effect and the Accumulation of CO2 in the Atmosphere of Venus". Nature 226: 1037-1039. doi:10.1038/2261037a0. ^ Venus - Stuart Robbins and David McDonald ^ Notes (created by Nick Strobel) for an introductory astronomy courses he teaches. Nick's new site Old site (The Wayback Machine) --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "geoengineering" group. 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