The link between clouds and circulation are at the heart of many of climate science's enduring riddles: How rapidly and how much will the Earth warm for a given forcing? How will circulations, from the storm tracks to the tropical rain-bands, change with warming, or how different were they in the past? What role does convective aggregation play in our climate system and does it matter for climate sensitivity? To what extent do cloud feedback processes also influence climate variability? These questions are at the heart of the Grand Science Challenge on Clouds Circulation and Climate Sensitivity and motivate our session. Observational and process studies that touch on these questions in ways that link to Earth System Modelling are also very welcome.