Carbon dioxide removal (CDR) is what puts the ‘net’ into ‘net zero emissions’. All pathways to limit global warming to 1.5–2 °C above pre-industrial levels that have been assessed by the Intergovernmental Panel on Climate Change require rapid decarbonization to start now. But they also require the removal of CO2 from the atmosphere because we won’t be able to eliminate carbon emissions entirely on the required time scales. ‘Hard to abate’ sectors such as aviation and shipping will remain large sources of greenhouse gases even in the most optimistic scenarios. Residual emissions will mean that we cannot achieve a zero-emissions goal, and we will need CDR to reach a net-zero target. Historically, this has meant planting or maintaining trees, but removing CO2 from the atmosphere and storing it in the ground, the ocean or in products will be more durable.