From 1971, Professor Hamanaka served for the Ministry of Environment, playing an active role in the field of environmental policy, specifically in topics such as air and water quality protection, and contributed to intergovernmental negotiations in areas including the Kyoto Protocol and its implementing rules. From 2001, he served as Vice-Minister for Global Environmental Affairs. He retired from the Ministry in 2004 and, in the same year, began teaching as a professor at Keio University, Faculty of Environment and Information Studies. He has served as the Chair of ICLEI Japan Office since July 2005. He served as the Chair of the Institute of Global Environmental Strategies Board of Directors from April 2007 to June 2017, and serves as Special Research Advisor since July 2017. Professor Hamanaka received a B.A. in Engineering from the University of Tokyo in 1967.