Climate hawk Bill McKibben wrote an important and influence Rolling Stone piece last July, “Global Warming’s Terrifying New Math.” He reduced the climate debate to “Three simple numbers that add up to global catastrophe — and that make clear who the real enemy is.”
CO2 emissions by fossil fuels (1 ppm CO2 ~ 2.12 GtC, where ppm is parts per million of CO2 in air and GtC is gigatons of carbon) via Hansen. Significantly exceeding 450 ppm risks several severe and irreversible warming impacts. We are headed toward 800 to 1,000+ ppm, which represents the near-certain destruction of modern civilization as we know it — as the recent scientific literature makes chillingly clear.
The three key numbers are:
- The First Number: 2° Celsius (3.6° Fahrenheit): The temperature rise we need to work as hard as possible to limit total warming to if we want to have our best chance of averting multiple catastrophes and amplifying carbon cycle feedbacks. (Equates to roughly 450 ppm CO2)
- The Second Number: 565 Gigatons: “Scientists estimate that humans can pour roughly 565 more gigatons of carbon … into the atmosphere by midcentury and still have some reasonable hope of staying below two degrees. (‘Reasonable,’ in this case, means four chances in five, or somewhat worse odds than playing Russian roulette with a six-shooter.)”
- The Third Number: 2,795 Gigatons: “This number is the scariest of all – one that, for the first time, meshes the political and scientific dimensions of our dilemma…. The number describes the amount of carbon already contained in the proven coal and oil and gas reserves of the fossil-fuel companies, and the countries (think Venezuela or Kuwait) that act like fossil-fuel companies. In short, it’s the fossil fuel we’re currently planning to burn.
ABC’s Nightline has done a terrific segment on McKibben’s math. I’d almost call it perfect, but they can’t quite get his name right!