Scientists attending the U.N. Framework Convention for Climate Change (UNFCCC) COP24 climate talks in Katowice, Poland, discussed potential solutions to slow global warming and stay below targets laid out in the 2015 Paris Agreement on climate change. Since 2005, REDD+ (Reducing Emissions from Deforestation and Forest Degradation) has been part of the negotiations, given the importance of forest protection and recovery in keeping global temperature rise below 1.5 degrees Celsius. So how much mitigation has REDD+, and other forest-based mitigation efforts achieved to guide efforts, so far? To address this question, Center International of Forestry Research (CIFOR) held an official side event at COP24 with partners from the Independent Evaluation Unit (IEU) of the Green Climate Fund (GCF), Wageningen University and the UN-REDD Programme to discuss the need for rigorous evidence on the impacts of forestry and land use interventions to promote transformational change.