Scientists identify '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.

The study came out of a 2005 meeting of 36 leading climate scientists who drew on the expertise of a further 52 specialists. It is believed to be the first time that scientists have attempted to assess the risks of what they have termed "tipping elements" in the Earth's climate system.