Climate tipping points have been the subject of much debate and confusion. Now Professor Tim Lenton of the University of East Anglia has published a very good piece, "Tipping points in the Earth System," giving some intellectual substance to the notion.
Not surprisingly, the tipping point Prof. Lenton worries about most is the disintegration of Greenland's ice sheet. He told The Guardian:
We know that ice sheets in the last ice age collapsed faster than any current models can capture, so our models are known to be too sluggish.
His paper examines where Greenland's tipping point is:
Our present warming commitment alone seems insufficient to tip any of the elements we have identified. However, it could get us close to the threshold for irreversible melt of the Greenland ice sheet. If that threshold is at the nearest end of its estimated error range (1°C further global warming) then it will be nearly impossible to avoid by mitigation unless we are lucky and the climate sensitivity is at the bottom end of its uncertainty range (circa 1.6°C warming for a doubling of pre-industrial CO2). If the threshold is further away (we estimate an upper limit of 2°C global warming) then mitigation would still need to be extremely aggressive to avoid it. Given this, it seems prudent to design long-term adaptation strategies in anticipation of a progressive melt of the Greenland ice sheet. Critically there remains an argument for mitigation even when the threshold is passed because the rate of GIS melt and the corresponding contribution to sea level rise depends on how far the threshold is exceeded.
Based on current information all the other potential tipping elements [which include the destruction of the Amazon rain forest and the disintegration of the West Antarctic Ice Sheet] might be avoided by limiting global warming to 2°C above pre-industrial (although we cannot be sure).
And that is as good an argument for limiting total warming as you'll find.
This post was created for ClimateProgress.org, a project of the Center for American Progress Action Fund.
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Comments View as Flat
JMG Posted 10:49 am
18 Aug 2007
The best book on tipping points
that I've found so far is "With Speed and Violence" by Fred Pierce. I just got it back from a friend, who used to be a science writer for the National Park Service (in the days when Creationist tracts weren't being offered in the Grand Canyon gift shops) -- she said she couldn't finish it because it frightened her for her grandchildren too much. It is not written that way--but the implications of the manifold carbon bombs with their fuses lit are definitely sobering.
Save the world: Reduce greenhouse gas emissions 5% annually.
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Colin Wright Posted 7:48 pm
18 Aug 2007
Thanks. A great readable paper, but ...
I wonder if it is superceded by Hansen's recent work on the "albedo flip property of ice/water". For instance, compare each author's words on the Greenland Ice Sheet.
Hansen:
Lenton:
Or on the West Antarctic Ice Sheet.
Hansen:
Lenton:
I'm no expert, and there could be no real contradictions here between the authors. But there does at least seem to be a difference of emphasis. The albedo-flip picture could be a more important, more holistic way to look at the Earth than a series of tipping points.
Incidentally, I heard on the radio today that the Arctic ice cap extent is at its smallest size ever -- yet we still have at least another month of summer melting to go.
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WWAGD?! Posted 1:30 am
19 Aug 2007
Greenland...mmm...
I'll have to put that on my list of now cheap places to buy land for my summer home. Alberta Canada is a strong contender. Ideally, I'd figure out where the land ends under the ice in the Northwest Territories and have waterfront property for water skiing on the Arctic Ocean.
John Bailo
Sutext:
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dobermanmacleod Posted 4:11 pm
19 Aug 2007
A more immediate tipping point
NASA defines abrupt climate change as the inability of the earth's eco-systems to keep pace with rapid climate change. In other words, it is predictable that soon, as the earth rapidly heats up from historically unprecidented increases in atmospheric greenhouse gas levels, the eco-systems that maintain the carbon balance will go into death spirals, resulting in abrupt climate change.
Furthermore, as carbon sinks will become carbon emitters BIG TIME, it will also result in runaway global warming.
In my opinion, the IPCC severely underestimated the rate of ocean rise due to melting ice caps and glaciers, but still that will be a slow motion tipping point. Instead, we should be very concerned about the carrying capacity of the earth abruptly dropping in the next couple of decades.
There are historical examples of more mild abrupt climate changes, and they resulted in famine, war, pestilence, and death (the Four Horsemen). The difference is we now have a thousand times more people, and weapons of mass destruction.
Frankly, worrying about the ice caps and glaciers melting is rather naive, when the eco-systems that regulate the carbon budget are collapsing. This is just like the false assumption that mankind will be able to so drastically cut their emissions so fast as to be able to avoid either abrupt climate change or runaway global warming.
Unless you find a cost effective way to start removing the excess CO2 from the air soon, it is all over. The gigantic cost of completely rebuilding our energy infrastructure is predictably causing political gridlock. Developing countries will continue to rapidly increase their emissions to "catch up" with developed countries. Besides, nature will predictably reduce her ability to remove the CO2 from the air (a decline of 30% by 2030 has been forecast).
Yeah, go on believing that the tipping point to fear most is the rise of ocean levels-ha! One faulty paradigm after another...perhaps mankind is too stupid to be sparred the approaching bottleneck?
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MarkUK Posted 8:02 pm
19 Aug 2007
sure
"the eco-systems that regulate the carbon budget are collapsing"
But they're not.
Let's not pretend we know exactly what is going to happen.
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