RealClimate has a great post up on climate "tipping points," a notion that has been used and abused with great frequency lately by laymen and journalists -- including yours truly. It goes into detail picking apart positive feedbacks, tipping points, and points of no return.
The most valuable bit for me was clarifying what James Hansen has in mind when he says that we have ten years to fundamentally change course:
The '10 year' horizon is the point by which serious efforts will need to have started to move the trajectory of concentrations away from business-as-usual towards the alternative scenario if the ultimate warming is to stay below 'dangerous levels'. Is it realistic timescale? That is very difficult to judge. Wrapped up in the '10 year' horizon are considerations of continued emission growth, climate sensitivity, assumptions about future volcanic eruptions and solar activity etc. ... While the '10 years' shouldn't be read as an exact timetable, it is surely in the right ballpark. 30 more years of business-as-usual will make it impossible to keep temperatures from rising beyond Eemian levels (see here for some discussion of stabilisation scenarios), and decisions (on infrastructure, power stations, R&D, etc.) that are being made now will determine the emissions for decades to come.
As the post goes on to explain, there isn't so much a single tipping point as a variety of tipping points at various levels, some more dangerous than others, some more reversible than others.
Of course, what matters most at this point are not the purely physical tipping points but the ones that involve us. When will our concern pass the threshold of serious action? Nobody can predict that for us.
VIDEO: Violent Massey attack on Goldman Prize winner Judy Bonds
Comments View as Flat
bookerly Posted 10:19 am
07 Jul 2006
Beware
The danger of letting people think that they have ten years before "serious efforts need to have started" should be obvious.
For many people, that means they don't have to "start" to think about the problem for ten years.
That the process of deciding what to do doesn't need to "start" for ten years.
That the planning for what to do doesn't need to "start" for ten years.
Not what I think Dr. Hansen has in mind, but a real danger to beware of in terms of discussion.
patrick
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ffletcher Posted 10:35 am
07 Jul 2006
Tipping Points May Be Key To Setting Policy
These tipping points may be the key to intelligent policy making regarding reductions in CO2 and other behaviors that drive global warming.
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caniscandida Posted 6:56 pm
07 Jul 2006
misrepresenting James Hansen
Yes, Patrick, you are quite right. "We do not really need to start serious efforts for another ten years" is not at all the same as "We need to have begun serious efforts within the next ten years." To me at least, James Hansen seems to be saying something like the latter statement. But no doubt his advice is even now being misrepresented to sound like the former.
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