Image courtesy of soham_pablo via flickr
While the signs of unimpeded climate change already seem to be all around us - from the melting Arctic to the growing number of drought-stricken regions - we haven't yet reached what scientists identify as its "tipping points" - ways in which the planet could tip into a dangerous state that could endure for many centuries. As The Independent's Steve Connor notes in a recent article, that day may not be far off.
In a major new study published in the Proceedings of the National Academy of Sciences, scientists have identified nine scenarios under which the Earth could be tipped into a catastrophic state - most of which will likely occur within the next century. They warn that these will essentially become irreversible on a human timescale once they pass a particular threshold; the changes these scenarios will precipitate would be felt for many centuries to come.Timothy Lenton of the University of East Anglia, who authored the study, said it was still possible to avoid these tipping points if significant cuts are made in greenhouse gas emissions though he warned that time is running short. He explained that we will likely need to adapt to the planet's changing conditions and that we should immediately focus on designing an early-warning system that could detect some of these points before it's too late. The nine, irreversible elements are:
* 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.