Clouds are highly significant in our climate system. But what is the exact role they play? And how is that role changing with rising temperatures? Answering these questions makes a major contribution to understanding the processes underlying climate change. The French climatologist Sandrine Bony investigates the role of clouds in the climate system, and specifically in climate change. For her pioneering work in this field, the Academy is awarding her this year's Buys Ballot Medal for meteorology, in particular climate change.