The Coming Global Climate–Technology Revolution

S uppose that averting dangerous climate change meant limiting the concentration of greenhouse gases (measured in parts per million, or ppm, by volume) in the atmosphere so that the world faced a temperature increase of no more than 2°C—a goal endorsed by the European Union. What would it take to meet this goal? Because of “climate uncertainty,” we cannot be sure. We can meet the goal with probability greater than 90 percent by limiting concentrations to 350 ppm carbon dioxide “equivalent” (the concentration of carbon dioxide that would cause the same amount of “radiative forcing” as a given mixture of carbon dioxide, or CO2, and other greenhouse gases), but we have already overshot that level (Anderson and Bows, 2008, p. 2). We can meet the goal with probability close to 50 percent by stabilizing concentrations at 450 ppm CO2 equivalent, but to do that will require that global net emissions (additions to the atmosphere minus subtractions) peak by around 2015, decline rapidly after that time, and reach zero soon after 2050. We can abandon the 2°C target and accept the likelihood of greater climate change; but stabilization at some other level, like 550, or 650, or even 750 ppm of CO2 equivalent will also require radical reductions in emissions. Emissions of CO2 and other greenhouse gases can be reduced significantly using existing technologies, but stabilizing concentrations will require a technological revolution—a “revolution” because it will require fundamental change, achieved within a relatively short period of time.