Independent UK: Nine Tipping Points Of Global Warming

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http://www.alternet.org/environment/76053

Global Warming: Nine Things that Will Put us Over the Edge

By Steve Connor, The Independent UK. Posted February 8, 2008.

Scientists have identified nine 'tipping points' of climate change.

Nine ways in which the Earth could be tipped into a potentially dangerous state that could last for many centuries have been identified by scientists investigating how quickly global warming could run out of control.

A major international investigation by dozens of leading climate scientists has found that the "tipping points" for all nine scenarios -- such as the melting of the Arctic sea ice or the disappearance of the Amazon rainforest -- could occur within the next 100 years.

The scientists warn that climate change is likely to result in sudden and dramatic changes to some of the major geophysical elements of the Earth if global average temperatures continue to rise as a result of the predicted increase in emissions of man-made greenhouse gases.

Most and probably all of the nine scenarios are likely to be irreversible on a human timescale once they pass a certain threshold of change, and the widespread effects of the transition to the new state will be felt for generations to come, the scientists said.

"Society may be lulled into a false sense of security by smooth projections of global change. Our synthesis of present knowledge suggests that a variety of tipping elements could reach their critical point within this century under anthropogenic (man-made) climate change," they report in the journal Proceedings of the National Academy of Sciences.

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A tipping point is defined as the point where a small increase in temperature or other change in the climate could trigger a disproportionately larger change in the future. Although there are many potential tipping points that could occur this century, it is still possible to avoid them with cuts in greenhouse gases, said Professor Lenton.

He added: "But we should be prepared to adapt ... and to design an early-warning system that alerts us to them in time."

Irreversible changes

* Arctic sea ice: some scientists believe that the tipping point for the total loss of summer sea ice is imminent.

* Greenland ice sheet: total melting could take 300 years or more but the tipping point that could see irreversible change might occur within 50 years.

* West Antarctic ice sheet: scientists believe it could unexpectedly collapse if it slips into the sea at its warming edges.

* Gulf Stream: few scientists believe it could be switched off completely this century but its collapse is a possibility.

* El Niño: the southern Pacific current may be affected by warmer seas, resulting in far-reaching climate change.

* Indian monsoon: relies on temperature difference between land and sea, which could be tipped off-balance by pollutants that cause localised cooling.

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