Climate change is the defining challenge of our time. This important document by the United Nations and global partner organizations, prepared under the auspices of the Science Advisory Group of the Climate Action Summit, features the latest critical data and scientific findings on the climate crisis.The Report provides a unified assessment of the state of our Earth system under the increasing influence of anthropogenic climate change, of humanity’s response thus far and of the far-reaching changes that science projects for our global climate in the future. The scientific data and findings presented in the report represent the very latest authoritative information on these topics. It is provided as a scientific contribution to the UN Climate Action Summit 2019, and highlights the urgent need for the development of concrete actions that halt the worst effects of climate change.