Sir Andrew Haines is Professor of Environmental Change and Public Health at the Centre for Climate Change and Planetary Health, London School of Hygiene and Tropical Medicine, where he was previously director between 2001 and 2010. He was member of the Intergovernmental Panel on Climate Change for the Second, Third, and Fifth Assessment Reports. He was chair of the Rockefeller/ Lancet Commission on Planetary Health in 2014–15, and chair of the Task Force on Climate Change Mitigation and Public Health in 2008–9. He is an international member of the US National Academy of Medicine. Howard Frumkin is Professor Emeritus of Environmental and Occupational Health Sciences at the University of Washington School of Public Health in Seattle, where he was dean from 2000 through 2006. He was previously head of the Wellcome Trust 'Our Planet, Our Health' initiative, and director of the National Center for Environmental Health at the US Centers for Disease Control and Prevention.