The aim of most people fighting global warming is to keep atmospheric carbon dioxide levels from increasing above 450ppm, which is approximately 65ppm above today’s levels. This target has been advocated by climate scientist James Hansen, the head of NASA’s Goddard Institute for Space Studies, and has been also been advocated by the UN’s Intergovernmental Panel on Climate Change. But Hansen is now saying that the target is too high. In an article in the British newspaper The Sunday Times he says:
“If humanity wants to preserve a climate resembling that in which civilisation developed, then the palaeoclimate evidence and ongoing climate change suggest CO2 must be reduced from its current level to between 300-350ppm. A 350ppm target is only achievable by phasing out coal use….We need a moratorium on the construction of coal-fired power plants and we must phase out the existing ones within two decades.”
If Hansen is right, it appears we will just have to accept a planet that does not resemble the one we are familiar with. Limiting CO2 to 450ppm appears to be an almost impossible task, particularly with China and India counting on coal to lift hundreds of millions of people out of a meager existence. Reducing CO2 to 350ppm or even lower doesn’t seem to be a feasible goal. It is hard to imagine the world only 20 years from now without any operating coal-fired plants. According to the article, Hansen will support his view of setting a lower target in a research paper. Until that paper is published and other scientists have a chance to review it is unlikely that the target of 450ppm will revised. However, perhaps we should be prepared for an even gloomier view of the possibility of extracting ourselves out of our global warming predicament than we now have.