Tipping point (climatology)
|This article may be expanded with text translated from the corresponding article in the Spanish Wikipedia. (February 2013)|
A climate tipping point is a somewhat ill-defined concept of 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 and/or West Antarctic 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 any acceleration of the warming process. Carbon dioxide as of May 2012[update] makes up 396.18 ppm of Earth's atmosphere and monitoring stations in the Arctic spring 2012 measuring more than 400 ppm of the heat-trapping gas in the atmosphere. James E. Hansen said that this tipping point had already been reached in April 2008 when the CO2 level was 385 ppm. (Hansen states 350 ppm as the upper limit.) "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.
Scientists and other specialists continue to express concern about global warming and irreversible tipping points. They have used metaphors such as "the door is closing" and warned of global food and water shortages, hundreds of millions of people being displaced by rising sea levels, and storms becoming ever more frequent and severe worldwide. Others have tried systematically to short-list large scale components of the Earth system that may be subject to tipping points, defining tipping points as a variety of phenomena, including the onset of positive feedback, hysteresis effects, and the possible effect of statistical noise at critical points.
- 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
See also 
- "NOAA ESRL DATA". NOAA. 7 May 2012. Retrieved 9 May 2012.
- Borenstein, Seth (31 May 2012). "Scientists: Carbon dixode at highest level in 800,000 years". USA Today. Associated Press.
- Earth in crisis, warns NASA's top climate scientist PhysOrg.com, April 07, 2008 . Accessed August 2008.
- Saunders, Marshall (22 April 2012). "Earth to mankind". The Gainesville Sun. Retrieved 9 May 2012.
- Lenton, T. M.; Held, H.; Kriegler, E.; Hall, J. W.; Lucht, W.; Rahmstorf, S.; Schellnhuber, H. J. (2008). "Tipping Elements in the Earth's Climate System". PNAS 105 (6): 1786–1793. doi:10.1073/pnas.0705414105.
- Ian Sample (11 August 2005). "Warming hits 'tipping point'". London: The Guardian. Retrieved 21 September 2009.
- Foley, Jonathan; Daily, Gretchen C.; Howarth, Robert; Vaccari, David A.; Morris, Adele C.; Lambin, Eric F.; Doney, Scott C.; Gleick, Peter H.; Fahey, David W. (April 2010). "Boundaries for a Healthy Planet". Scientific American.
- 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.
- Hansen, James (2008) (PDF of Slides). Global warming 20 years later: tipping points near (Speech). address to National Press Club, and United States House Select Committee on Energy Independence and Global Warming. Washington DC. http://www.columbia.edu/~jeh1/2008/TippingPointsNear_20080623.pdf.
- Adam, David (14 January 2010). "Arctic permafrost leaking methane at record levels". London: The Guardian.
- 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. Bibcode:2010Sci...327.1246S. doi:10.1126/science.1182221. PMID 20203047.
- "Study: Arctic seabed methane stores destabilizing, venting". Physorg. 4 March 2010.
- David Roberts (September 22, 2009). "Scientists identify "safe operating space for humanity" in seminal Nature study". Grist.org.
- What are climate ‘tipping points’? Big Picture TV video February 20, 2007, David Wasdell, Director of the Meridian Programme
- Billings, Lee (12 March 2010). "How the extinction of the dinosaurs, Arctic methane leaks, and nuclear weaponry reveal the precarious thresholds of life on Earth". Seed (magazine).
- Cascio, Jamais (9 March 2010). "Pushing Back Against the Methane Tipping Point". Worldchanging.
- Keim, Brandon (December 23, 2009). "7 Tipping Points That Could Transform Earth". Wired.com.
- Is Global Warming Happening Faster Than Expected? October 29, 2012 Scientific American
- Quick-Change Planet: Do Global Climate Tipping Points Exist? March 25, 2013 Scientific American