Tipping point (climatology)
A climate tipping point is a point when global climate changes from one stable state to another stable state, in a similar manner to a wine glass tipping over. After the tipping point has been passed, a transition to a new state occurs. The tipping event may be irreversible, comparable to wine spilling from the glass—standing up the glass will not put the wine back.
Global warming proceeds by changing the composition of gases in the Earth's atmosphere by the emission of greenhouse gases such as carbon dioxide and methane. As warming proceeds it brings about changes to the natural environment which may result in other changes. For example, warming may begin to melt the Greenland ice sheet. At some level of temperature rise, the melt of the entire ice sheet will become inevitable, even though complete melting may not occur for millennia. Thus a tipping point may be passed without any immediately obvious consequences. Nor does the use of tipping point necessarily imply any acceleration of the warming process.
James E. Hansen believes this point has already been reached with carbon dioxide levels currently at 391.7 ppm. "Further global warming of 1°C defines a critical threshold. Beyond that we will likely see changes that make Earth a different planet than the one we know." He has further suggested potential projections of Runaway climate change on Earth creating more Venus-like conditions in his book Storms of My Grandchildren.
Other scientists maintain the term is too vague for a non-linear system such as the Earth's climate, in which there may be transitions between several equilibrium states. It has been speculated that geoengineering may be used to reverse, prevent, or postpone a tipping point event.
Lenton et al. highlights a number of tipping points, including:
- Boreal forest dieback
- Amazon rainforest dieback
- Loss of Arctic and Antarctic sea ice (Polar ice packs) and melting of Greenland and Antarctic ice sheets
- Disruption to Indian and West African monsoon
- Formation of Atlantic deep water near the Arctic ocean, which is a component process of the thermohaline circulation.
- Loss of permafrost, leading to potential Arctic methane release and clathrate gun effect
- ^ Earth in crisis, warns NASA's top climate scientist PhysOrg.com, April 07, 2008 . Accessed August 2008.
- ^ Lenton, T. M.; Held, H.; Kriegler, E.; Hall, J. W.; Lucht, W.; Rahmstorf, S.; Schellnhuber, H. J. (Feb 2008). "Tipping elements in the Earth's climate system" (Free full text). Proceedings of the National Academy of Sciences 105 (6): 1786–1793. Bibcode 2008PNAS..105.1786L. doi:10.1073/pnas.0705414105. PMC 2538841. PMID 18258748. http://www.pnas.org/cgi/pmidlookup?view=long&pmid=18258748.
- ^ Ian Sample (11 August 2005). "Warming hits 'tipping point'". London: The Guardian. http://www.guardian.co.uk/environment/2005/aug/11/science.climatechange1. Retrieved 21 September 2009.
- "Boundaries for a Healthy Planet" by Jonathan Foley, Gretchen C. Daily, Robert Howarth, David A. Vaccari, Adele C. Morris, Eric F. Lambin, Scott C. Doney, Peter H. Gleick and David W. Fahey Scientific American April 2010
- Hansen, J. (2008). "Tipping point: Perspective of a climatologist". In Ward Woods. State of the Wild 2008-2009: A Global Portrait of Wildlife, Wildlands, and Oceans (State of the Wild). Washington, DC: Island Press. pp. 6–15. ISBN 1-59726-135-1. OCLC 429495689. http://pubs.giss.nasa.gov/abstracts/2008/Hansen_1.html.
- “Global warming 20 years later: tipping points near” (2008) PDF (address to National Press Club, and United States House Select Committee on Energy Independence and Global Warming, Washington DC [44 pages]:
- Adam, David (14 January 2010). "Arctic permafrost leaking methane at record levels". London: The Guardian. http://www.guardian.co.uk/environment/2010/jan/14/arctic-permafrost-methane.
- Shakhova, N; Semiletov, I; Salyuk, A; Yusupov, V; Kosmach, D; Gustafsson, O (5 March 2010). "Extensive Methane Venting to the Atmosphere from Sediments of the East Siberian Arctic Shelf". Science 327 (5970): 1246–50. doi:10.1126/science.1182221. PMID 20203047. http://www.sciencemag.org/cgi/content/abstract/327/5970/1246.
- "Study: Arctic seabed methane stores destabilizing, venting". Physorg. 4 March 2010. http://www.physorg.com/news186920485.html.
- David Roberts (September 22, 2009). "Scientists identify “safe operating space for humanity” in seminal Nature study". http://www.grist.org/article/2009-09-22-scientists-identify-safe-operating-space-for-humanity-nature.
- What are climate ‘tipping points’? Big Picture TV video February 20, 2007, David Wasdell, Director of the Meridian Programme
- "How the extinction of the dinosaurs, Arctic methane leaks, and nuclear weaponry reveal the precarious thresholds of life on Earth". Seed (magazine). http://seedmagazine.com/content/article/extinctions_tipping_points/.
- Jamais Cascio (9 March 2010). "Pushing Back Against the Methane Tipping Point". Worldchanging. http://www.worldchanging.com/archives/011016.html.
- Brandon Keim (December 23, 2009). "7 Tipping Points That Could Transform Earth". Wired.com. http://www.wired.com/wiredscience/2009/12/tipping-elements/.
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