Hans Joachim Schellnhuber (b.1950) is a German physicist, founding director of the Potsdam Institute for Climate Impact Research in 1991, Chair of the German Advisory Council on Global Change, Chair of Theoretical Physics at Potsdam University, Research Fellow at the Stockholm Resilience Center, Senior Advisor at the Institute for Advanced Sustainability Studies, Chief Advisor of Climate-KIC (Knowledge and Innovation Community), member of the 17-expert Earth League, and Chair of the EC High-Level Panel of European Decarbonization Pathways.  He has also served as a principal advisor to EU President Jose Manuel Barroso.  An expert on possible climate tipping points, Schellnhuber has published >50 books and 250 articles, including World in Transition: Fighting Poverty Through Environmental Policy (2004), “A Safe Operating Space for Humanity” (Nature, 2009; with Johan Rockström and 23 others, on planetary boundaries), Climate Change as a Security Risk (2009), Turn Down the Heat (lead author of 2012 World Bank report on possible 4^oC warming by end of 21C), and “A Roadmap for Rapid Decarbonization” (Science, 2017; with Johan Rockström et al).  He has been widely honored, e.g.: the Royal Society Wolfson Research Merit Award (2002), German Environment Prize (2007), Volvo Environment Prize (2011), and Blue Planet Prize (2017).