There’s No Ultimate Tipping Point

Ray on a response on RealClimate says nicely something I have been trying to say to the doomsayers:

Edward Greisch: See the chart on page 274 of “Six Degrees” by Mark Lynas. Mark Lynas says we have until 2015 to BEGIN REDUCING our total CO2 output and we have until 2050 to actually reduce our CO2 output by 90%. Mark Lynas says if we don’t follow the schedule in Six Degrees, we will encounter positive feedbacks which will take the control of the climate out of our hands. Civilization may fall anyway well before 2050, but we can avoid going extinct by 2100. Mark Lynas says we have to hold the CO2 level to 400 parts per million to have a 75% chance of avoiding the positive feedbacks. Is Mark Lynas correct? 8 years is a very tough timetable to stop the building of coal fired power plants and replace some coal fired power plants with nuclear. I doubt that anything else other than a plague that kills a few billion people could make a dent within 8 years.

[Response: From other estimates I’ve seen, Lynas’ timetable seems about right if the goal is to avoid 450 ppm. To avoid 400ppm, even his timetable is a bit of a stretch. However, with regard to the impacts of exceeding 400ppm (or even 450ppm), if you are quoting Lynas correctly I would differ with his assessment. There is no magic threshold crossed at 450 that commits us suddenly to the kind of catastrophic changes you mention, and certainly not to extinction of humanity by 2100. If we can’t hold the line at 450, there are still harms to be avoided by stopping short of doubling. If we can’t stop doubling, there are still harms to be avoided by preventing tripling, and so forth. But his general sentiment that we can’t drag our feet on this is correct. –raypierre]

No matter what the circumstance, unless we are finally extinct, there is always a best we can do. We should strive in our imperfect way to stay close to that.


  1. Amazing. Following the link to “Candy Jordan’s” Blogger Profile leads to a claim of a PhD in atmpospheric science. Odd that the comment read as if it came from a fourteen year old. “Jordan” claims a doctorate from the “Department of Applied Physics at the University of Chicago” (no such department exists). The first Google hit linking a Candace Jordan to the University of Chicago shows that both names made small donations to a medical charity in 2006. The first google hit linking a Candace Jordan to “climate” yields a feng shui consultant.Since this is just childish trolling, I have removed my previous response.

  2. Dont’cha think – that some indication of a possible “catastrophe” would be evidenced in the history of the climate, when CO2 levels became high (following periods of warming)? Isn’t it remarkable – that in all history we see no dramatic changes resulting from this? Nothing? Do the doomsdayers think this is like a bomb or something – it either explodes or it does nothing? And why couldn’t IPCC analysis correctly predict the (favorable) outcome of the historical climate? Is it possible that IPCC analysis is biased about what will happen with CO2 in the atmosphere?

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