As Managing Director, Lewis oversees strategic development, program implementation, and staff management at Hot or Cool. Previously, Lewis has served as Executive Director of SEED, founded as a UN partnership at the 2002 World Summit on Sustainable Development to promote entrepreneurship for sustainable development. Prior to that, he was Director for Sustainable Consumption and Production at the think tank Institute for Global Environmental Strategies. He has consulted with organizations including United Nations agencies, the Asian and African Development Banks, the European Commission, the Association of Southeast Asian Nations (ASEAN), and has served as technical or science-policy adviser to several national government delegations, including Finland, Japan, Sweden, Indonesia, Hungary. Lewis conceived and led the 1.5-Degree Lifestyles project, analysing potential contribution of lifestyle changes to the aspirational 1.5 °C target under the Paris Agreement on climate change. He co-led the United Nations One Planet programme on Sustainable Lifestyles and Education. He has an M.Sc. Sustainable Resource Management (Technical University Munich, Germany) and a Ph.D. Political Economy (University of Helsinki, Finland).