He was also a leading scientific contributor to the establishment of the Climate and Clean Air Coalition, a group of now more than 60 nations along with many intergovernmental and non-governmental organization dedicated to implementing actions that simultaneously reduce air pollution and mitigate climate change. He chaired the 2011 Integrated Assessment of Black Carbon and Tropospheric Ozone produced by the United Nations Environment Programme and World Meteorological Organization that, along with the paper in "Science" he led in 2012 entitled ""Simultaneously Mitigating Near-Term Climate Change and Improving Human Health and Food Security"" helped to catalyze the Coalition's formation. He has served as Chair of the Science Advisory Panel to the Coalition since 2012.