Must-have slide No. 1: The narrow temperature window that gave us modern human civilization
I am starting a new feature and a new category for must-have PowerPoint slides. I’ll begin with my favorite new slide, which shows just how stable the climate has been over the 10,000-year period that allowed modern human civilization to develop and flourish (click figure for larger version):
The slide is a must-have because it captures the risk we are taking while also providing a quick visual rebuttal to a very common denier talking point, one that NASA administrator Michael Griffin of all people repeated last year:
To assume that [global warming] is a problem is to assume that the state of Earth’s climate today is the optimal climate, the best climate that we could have or ever have had and that we need to take steps to make sure that it doesn’t change … I guess I would ask which human beings — where and when — are to be accorded the privilege of deciding that this particular climate that we have right here today, right now is the best climate for all other human beings. I think that’s a rather arrogant position for people to take.
Seriously! Needless to say, his employee, James Hansen rightly called those remarks “ignorant and arrogant.” He might have added “suicidal.”
So I had to have this slide after I saw it in a recent presentation from my friend Bob Corell, chair of the Arctic Climate Impact Assessment and now director of Global Change Programs at the Heinz Center.
And it’s not just Griffin pushing this nonsense. One of the Cato Institute climate experts currently debating online, Indur Goklany, just advanced the following argument against my call to stabilize at 450 ppm or less:
… There is no guarantee that stabilizing CO2 at 450 ppm would optimize human or environmental well-being. For all we know, stabilizing at 750 may be more optimal.
For all we know, Cato Institute might be funded by manufacturers of flood levees and desalination plants. Seriously, where does Cato find these guys? You can read my full reply to his absurd and disingenuous arguments here. I used Correll’s figure in the reply, which was a major inspiration for me to finally get off my butt and start this feature. (Note to self: Actually, you stayed on your butt the entire time you wrote this post.)
One key explanatory background note if you use the slide: The IPCC forecast of a total of 2Â°C to 3Â°C is based on stabilizing atmospheric concentrations of CO2 around 550 ppm (a doubling from pre-industrial levels of 280), up from 385 today. The “band of uncertainty” involves the uncertainty about the climate sensitivity to a doubling of CO2 (absent the slow feedbacks). But as I have noted here before, the longer-term climate sensitivity to a doubling is probably much higher. In any case, we are headed to much more than 550 ppm this century. As the IPCC’s latest assessment makes clear, anything other than a sharp and rapid reversal in greenhouse gas emissions trends risks warming this century of 4Â°C or more.