Arguments for and against climate tipping points

April 5, 2009


The New York Times has an interesting summary on the debate over climate “tipping points” amongst some scientists.

Climate tipping points, such as the collapse of the Atlantic thermohaline circulation system, are a fascinating and attention grabbing aspect of climate change science.  They bring to mind images of walls of water off the coast of New York, rushing in to destroy civilization as we know it overnight.

Despite their drama, scientists generally argue that relatively little is known about them and that which is known suggests that they are unlikely to occur overnight.  They could occur within our lifetimes, however, if warming trends continue.  And they could have just as devastating effect on our civilization as a wall of water 100 meters high.

State of the science

The most well known work on tipping points comes from Prof Tim Lenton of the School of Environmental Sciences and colleagues at the Postdam Institute of Climate Impact Research (PIK), Carnegie Mellon University, Newcastle University and Oxford University.

They have a “short list”  of nine tipping elements, all of them could be tipped within the next 100 years.  The nine tipping elements and the time it would take to tip are:


  • Melting of Arctic sea-ice (approx 10 years)
  • Decay of the Greenland ice sheet (more than 300 years)
  • Collapse of the West Antarctic ice sheet (more than 300 years)
  • Collapse of the Atlantic thermohaline circulation (approx 100 years)
  • Increase in the El Nino Southern Oscillation (approx 100 years)
  • Collapse of the Indian summer monsoon (approx 1 year)
  • Greening of the Sahara/Sahel and disruption of the West African monsoon (approx 10 years)
  • Dieback of the Amazon rainforest (approx 50 years)
  • Dieback of the Boreal Forest (approx 50 years)


These are generally the kinds of things which are meant when scientists talk about “dangerous climate change”.  If some of the worse ones were to occur, our entire food, water and weather systems would be thrown so far out of balance that we’d be likely to suffer the kinds of massive die-offs suggested by James Lovelock in recent days.

In a press release, Prof Lenton suggests;

Society must not be lulled into a false sense of security by smooth projections of global change,” said Prof Lenton. “Our findings suggest that a variety of tipping elements could reach their critical point within this century under human-induced climate change. The greatest threats are tipping of the Arctic sea-ice and the Greenland ice sheet, and at least five other elements could surprise us by exhibiting a nearby tipping point.

ScienceDaily has an excellent summary, sorting these events by probability and magnitude.

Full research excerpt here.