Climate change caused by human activity will have devastating effects on the biosphere, increasing the frequency of natural disasters, displacing communities, and destroying habitats. Global efforts to reduce dependance on fossil fuels and curb greenhouse gas emissions may not be sufficient to avert catastrophe. We must therefore consider approaches that actively sequester carbon from the atmosphere alongside a switch to clean energy and changes in lifestyle. The authors of this volume present a series of proposals for tackling climate change using synthetic biology approaches with the potential to work at scale. These include genetic engineering of crops and forest plants, the use of bacteria to capture methane and accelerate mineral weathering to draw down carbon dioxide, and development of biological nitrification inhibitors to reduce nitrate production and ozone depletion. They also discuss the regulatory challenges and policy obstacles to implementation of these technologies, arguing that bold corrective action is needed to avoid irreversible and insufferable planetary warming.