Cli-Mates ran from April 2017 until March 2019 targeting young people who have the most to lose in the course of climate change. Young adults are an important target group to engage in the deep societal transformation necessary to limit global warming. Cli-Mates engaged 18 to 29 year olds in elaborating social norms, self-efficacy, peer-inspiration as well as group efficacy for mainstreaming climate action among young adults. By combining climate and communication science, arts and design, the Cli-Mates team developed new creative methods and communication formats together with young adults in a co-creation process to stimulate youth collective action on climate change.