In this 2007 study of tipping points the Arctic sea ice concluded that the greatest (and clearest) threat of all tipping points is to the Arctic with summer sea-ice loss
T. Lenton H Held , E Kriegler JW. Hall , W Lucht, S Rahmstorf , and H J Schellnhuber.
Arctic Tipping Points Prof. Carlos Duarte
Duarte, C.M., Lenton, T., Wadhams, P., Wassmann, P. (2012). Abrupt climate change in the Arctic. Nature Climate Change
Arctic Ice Cover , Ice Thickness and Tipping Points. Peter Wadhams Ambio 2012
In a 2012 paper A recent tipping point in the Arctic sea-ice cover: abrupt and persistent increase in the seasonal cycle since 2007 Prof Tim Lenton a tipping point expert concluded that the Arctic summer sea ice had indeed passed its tipping point at the sudden record 2007 loss.
Definition A tipping point can most easily be defined as a small change that can have a large effect on the end state of a system. For example, we have the well known proverb of ‘the straw that breaks the camel’s back’.
Most of the planetary tipping points involve the Arctic- as can be seen fromthe tiping global maps.
Unchecked Climate change will put world at ‘tipping point’.
The world’s diverse regions and ecosystems are close to reaching temperature thresholds – or “tipping points” – that can unleash devastating environmental, social and economic change WWF and Allianz report says 23 November 2009 Changes related to global warming are likely to be much more abrupt and unpredictable – and they could create huge social and environmental problems and cost the world hundreds of billions of dollars. “If we don’t take immediate action against climate change, we are in grave danger of disruptive and devastating changes,” said Kim Carstensen, the Head of WWF Global Climate Initiative. “Reaching a tipping point means losing something forever. This must be a strong argument for world leaders to agree a strong and binding climate deal in Copenhagen in December. According to the report, carried out by the Tyndall Centre, the impacts of passing “Tipping Points” on the livelihood of people and economic assets have been underestimated so far.
Without immediate climate action, sea level rise on the East Coast of the USA, the shift to an arid climate in California, disturbances of the Indian Summer Monsoon in India and Nepal or the dieback of the Amazon rainforest due to increasing drought, are likely to affect hundreds millions of people and cost hundreds of billions of dollar
The term tipping point is most typically used in the context of climate change and its consequences to describe situations where the climate system-encompassing the atmosphere, oceans, land, cryosphere6, and biosphere-reaches a point at which there is a disproportionately large, singular response (e.g., a phase transition) as a result of only a moderate additional change in the inputs to the system (e.g., an increase in the CO2 concentration). Exceeding one or more tipping points could potentially result in abrupt changes in the climate or any component of the climate system.
A tipping point is defined in Alley et al. (2002)7 to "occur when the climate system is forced to cross some threshold, triggering a translation to a new state at a rate determined by the climate system itself and faster than the cause." These changes would produce impacts at a rate and intensity far greater than slow and steady changes currently being observed (and in some cases, planned for) in the climate system.
2009 WWF Allianz Major Tipping Points in the Earth’s Climate System Consequences Insurance