When it comes to slowing the warming of our planet, there is no substitute for immediate, dramatic reductions in anthropogenic greenhouse gas emissions. But emissions reductions alone won’t be enough to limit warming to the 1.5 degrees Celsius goal at the heart of the 2015 Paris Agreement, or even to the Agreement’s upper limit of 2 degrees Celsius. In fact, we’ll almost certainly need to complement emissions reductions with big investments in carbon dioxide removal, or CDR, to capture and lock away some of the carbon dioxide we’ve already emitted.