Tipping point (climatology)

For other uses, see Tipping point (disambiguation).
Rate of Greenland ice sheet melt

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.

Definition

The IPCC AR5 report stated with medium confidence that precise levels of climate change sufficient to trigger a tipping point, defined as a threshold for abrupt and irreversible change, remain uncertain, and that the risk associated with crossing multiple tipping points increases with rising temperature.[1]

Outline

Global warming proceeds by changing the composition of gases in the Earth's atmosphere and Oceans 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; but the ice sheet itself may persist for millennia . A tipping point may be passed without any immediately obvious consequences, nor any acceleration of the warming process. Carbon dioxide as of May 2012 makes up 396.18 ppm of Earth's atmosphere[2] and monitoring stations in the Arctic spring 2012 measuring more than 400 ppm of the heat-trapping gas in the atmosphere.[3] 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."[4] He has further suggested potential projections of runaway climate change on Earth, in his book Storms of My Grandchildren.

Some scientists and other specialists sometimes express concern about global warming and irreversible tipping points, and use metaphors such as "the door is closing"[5] and warned of global food and water shortages, hundreds of millions of people being displaced by rising sea levels, famine, unhealthy and unlivable conditions, and storms becoming ever more frequent and severe worldwide.[6]

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.[7]

Arctic sea ice

In 2013, a study noted that there is an ongoing debate if Arctic sea ice has already passed a "tipping point", or if it is likely in the future. They pointed out, "Several recent studies argue that the loss of summer sea ice does not involve an irreversible bifurcation, because it is highly reversible in models". The study identified in 2007 abrupt transition in seasonal variability which persisted since then, and made a distinction between bifurcation and non-bifurcation `tipping point'.[8]

Examples

Lenton et al.2008 highlights a number of tipping elements,[7] including:

See also

References

  1. ↑ IPCC AR5 WGII (2014). "Climate change 2014, Impacts, Adaptation and Vulnerability" (PDF).
  2. ↑ "NOAA ESRL DATA". NOAA. 7 May 2012. Retrieved 9 May 2012.
  3. ↑ Borenstein, Seth (31 May 2012). "Scientists: Carbon dioxide at highest level in 800,000 years". USA Today. Associated Press.
  4. ↑ Earth in crisis, warns NASA's top climate scientist PhysOrg.com, April 07, 2008 . Accessed August 2008.
  5. ↑ Luderer, Gunnar; Pietzcker, Robert C; Bertram, Christoph; Kriegler, Elmar; Meinshausen, Malte; Edenhofer, Ottmar (1 September 2013). "Economic mitigation challenges: how further delay closes the door for achieving climate targets". Environmental Research Letters. 8 (3): 034033. doi:10.1088/1748-9326/8/3/034033.
  6. ↑ Saunders, Marshall (22 April 2012). "Earth to mankind". The Gainesville Sun. Retrieved 9 May 2012.
  7. 1 2 Lenton, T. M.; Held, H.; Kriegler, E.; Hall, J. W.; Lucht, W.; Rahmstorf, S.; Schellnhuber, H. J. (2008). "Inaugural Article: Tipping elements in the Earth's climate system". Proceedings of the National Academy of Sciences. 105 (6): 1786. doi:10.1073/pnas.0705414105.
  8. ↑ Valerie N. Livina, Timothy M. Lenton (2013). "A recent tipping point in the Arctic sea-ice cover: abrupt and persistent increase in the seasonal cycle since 2007". arXiv:1204.5445Freely accessible. doi:10.5194/tc-7-275-2013.
  9. ↑ Ian Sample (11 August 2005). "Warming hits 'tipping point'". London: The Guardian. Retrieved 21 September 2009.

External links

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