Hans Joachim "John" Schellnhuber CBE (born June 7, 1950) is the Director of Potsdam Institute for Climate Impact Research (PIK, University of Potsdam, Germany) and was Chief Government Advisor on Climate and Related Issues during Germany's EU Council Presidency and G8 Presidency. He has a Doctorate in Theoretical Physics from the University of Regensburg. Since 1992, he has been one of nine members of the German Advisory Council on Global Change (see: http://en.wikipedia.org/wiki/Hans_Joachim_Schellnhuber ).
Professor Schellnhuber (Director, Potsdam Institute for Climate Impact Research, Germany) says that for a 67% chance of avoiding a 2 degrees Centigrade temperature rise (would you get on a plane with only a 67% chance of it not crashing?) the World must have zero carbon dioxide (CO2) emissions by 2050 and must achieve this with a global annual per capita average of about 2.6 tonnes CO2 per person per year over the next 40 years. For leading annual; per capita CO2 polluters like the US and Australia this means that they must get to zero CO2 emissions by about 2020 (Germany by 2031, China by 2038, India and Burkina Faso by 2049). [1].
[1]. Hans Joachim Schellnhuber, Figure, “Emissions paths per capita for selected countries” in “Terra quasi-incognita: beyond the 2oC line”, 4 degrees and Beyond, International Climate Conference, 28-30 September 2009, Oxford, UK: http://www.eci.ox.ac.uk/4degrees/ppt/1-1schellnhuber.pdf .