Guus Velders, the Professor of ‘Air Quality and Climate Interactions’ at Utrecht University, is an atmospheric scientist who had essential roles in many of the world’s most important policy deals to reduce dangerous pollutants and fight global warming. As world-leading expert in the field of extremely potent greenhouse gases called hydrofluorocarbons (HFCs), he was one of the key figures who provided the scientific basis for the success of the 2016 Paris climate accord and important amendments to earlier climate deals such as the 1987 Montréal protocol. His long-standing dedication to the cause of climate change put him on Nature’s top 10 scientists in 2016 and Time’s 100 most influential people in 2017.