Scientists may have to turn back time and clean the atmosphere of all man-made carbon dioxide to prevent the worst impacts of global warming, one of Europe's most senior climate scientists has warned.
Professor John Schellnhuber, director of the Potsdam Institute for Climate Impact Research in Germany, told the Guardian that only a return to pre-industrial levels of CO2 would be enough to guarantee a safe future for the planet. He said that current political targets to slow the growth in emissions and stabilise carbon levels were insufficient, and that ways may have to be found to actively remove CO2 from the air.
Schellnhuber said: "We have to start pondering that it might not be enough to stabilise carbon levels. We should not rule out that it might be necessary to bring them down again."
Carbon levels have fluctuated over the last few hundred thousand years, but have rarely gone much beyond 280 parts per million (ppm), which is commonly referred to as the pre-industrial concentration. Over the last few centuries, human emissions of greenhouse gases have forced that concentration up as high as 387ppm, and it is rising at more than 2ppm each year.
World governments are currently trying to agree a deal that would restrict emissions and stabilise carbon levels at 450ppm, in an effort to limit global temperatures to 2C warmer than pre-industrial times.
Schellnhuber, who has advised the German government and European Commission on climate, said: "It is a compromise between ambition and feasibility. A rise of 2C could avoid some of the big environmental disasters, but it is still only a compromise."