On November 16, 2016, on the margins of COP22, the Yale Data-Driven Environmental Solutions Group, The Stanley Foundation, and the Galvanizing the Groundswell of Climate Action (GGCA) Coalition, in collaboration with the UNFCCC secretariat, held a workshop for data providers, analysts, and researchers. This forum focused on discussing opportunities for participants to collaborate on harmonizing and aggregating data on sub-national (i.e., city, state and region) and non-state (i.e., business, investor and civil society) climate action. Participants discussed current goals and challenges in their work to support and understand the rapidly expanding landscape of sub-national and non-state climate action. This short summary synthesizes the discussion, from the perspective of the GGCA.