*Alessandro Pelizzon* # Progressive Summary # Definitions # Chapter Notes ## Climate Disruptions and the Coming Dark Age > Hansen indicates that the ideal upward CO2 limit is 350 parts per million (ppm—a figure revised down from an initial 450), a number later popularized by American environmentalist Bill McKibben’s initiative 350.org. > The most current observations (2024) from the Mauna Loa observatory in Hawaii, however, mark atmospheric CO2 at over 426 ppm. > Curt Stager suggests that, depending on the amount of carbon ultimately released in the atmosphere, a return to its pre-industrial amounts may take between 400,000 and 500,000 years # Quotes # References