[Independent] 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.
* 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.
* West African monsoon: in the past it has changed, causing the greening of the Sahara, but in the future it could cause droughts.
* Amazon rainforest: a warmer world and further deforestation may cause a collapse of the rain supporting this ecosystem.
* Boreal forests: cold-adapted trees of Siberia and Canada are dying as temperatures rise.