Hans Joachim "John" Schellnhuber (born 7 June 1950) is a German atmospheric physicist, climatologist and founding director of the Potsdam Institute for Climate Impact Research (PIK) and former chair of the German Advisory Council on Global Change (WBGU). Education Schellnhuber studied mathematics and physics, obtaining a doctorate in theoretical physics from the University of Regensburg in 1980, followed in 1985 by habilitation (qualification for office) in theoretical physics at the University of Oldenburg. In 1981, he became a postdoctoral fellow at the Institute of Theoretical Physics (ITP) at the University of California, Santa Barbara, working across the corridor from its director Walter Kohn, who became one of his academic supervisors. Career Originally interested in solid state physics and quantum mechanics, Schellnhuber became drawn to complex systems and nonlinearity or chaos theory. As a full professor for theoretical physics and then director at the Institute for Chemistry and Biology of the Marine Environment at Oldenburg University, he was involved in analysing the structure of ocean currents. In 1991, he was called upon to create the Potsdam Institute for Climate Impact Research (PIK), and became its director in 1993 – making it grow from zero to one of the world's most renowned climate research institutes with today more than 300 employees following an interdisciplinary approach. As early as 1995 Schellnhuber proposed the 2 °C guardrail for global warming which was adopted first by the German government and the European Union and then, following the Copenhagen accord in 2009, as a global target by governments worldwide. From 2001–2005 Schellnhuber served as research director of the Tyndall Centre in England and became a visiting professor at the University of Oxford. Schellnhuber has been professor at the University of Potsdam, Germany, and an external professor at the Santa Fe Institute in the US. As a long-standing member of the Intergovernmental Panel on Climate Change which was jointly awarded the 2007 Nobel Peace Prize, Schellnhuber has been a coordinating lead author of the synthesis chapter of Working Group II of the IPCC's Third Assessment Report. He has warned of dire consequences of continued global warming As an expert on climatological tipping points, he is a public speaker on the subject. In 2017, Schellnhuber said that unless climate action is taken by 2020, the world "may be fatally wounded." Achievements Schellnhuber has helped create numerous iconic concepts such as the analysis of tipping elements in the climate