"the current level of CO2 in the atmosphere is already at 390 parts per million, even as the amount of methane in the atmosphere has been spiking in the last two years. In other words, we’re over the edge already. We’re no longer capable of “preventing” global warming, only (maybe) preventing it on such a large scale that it takes down all our civilizations."
http://salon.com/news/global_warming/index.html?story=/opinion/feature/2009/12/07/copenhagen