McKibben Must-Read: The Case For Fossil-Fuel Divestment: How Long Will Colleges Keep Investing in Companies Whose Stock Price Is Based on the Destruction of a Livable Climate? 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 [...]/p