Reversing climate change on Earth is the most important geodesign problem. The International Geodesign Collaboration, with the Liechtenstein Institute for Strategic Development, Geodesign hub and Esri, have launched a Global Climate Geodesign Challenge. This initiative has developed science-based tools and methods that will enable local, regional and global planners and decision-makers to address the full implications of climate change – negotiating and applying actions to reduce excessive atmospheric greenhouse gas concentrations via emission reduction and carbon sink enhancement. As part of this broader initiative, the University of Southern California has undertaken a pilot study of 300,000 km2 of Southern California integrating Esri’s Geoplanner, ArcGIS Online and carbon assessments, the Geodesign hub negotiation platform and the Liechtenstein Institute for Strategic Development’s Climate Actions. A global-local-global study follows to showcase geodesign’s role in reversing devastating climate change. The International Geodesign Collaboration is open to teams who want to participate in this project.