0-gigaton-scale negative emissions are necessary in essentially every emissions reduction scenario. We have no choice but to fund, research, and deploy them if we’re serious about keeping warming to 2 degrees; or close to it. We are not even close to on track.

The interest in CDR is growing. Why is this? Because it is becoming apparent that we are not going to reduce our CO2 emissions fast enough to avoid surpassing the 2°C goal. As a result, if we exceed the carbon budget associated with 2°C warming, CDR technologies could remove CO2 from the atmosphere to bring the carbon budget back into balance.

It’s very unlikely any one category of technology, or any one natural approach, will scale enough. We should think of a portfolio across all the approaches outlined here, as well as more I didn’t discuss or have yet to be discovered.