Former Secretary of Energy Stephen Chu at Climate One in 2016.

We’ve made progress, but it is nowhere near fast enough. The internal combustion engine is on life support. Fossil fuel energy sources and companies are stranded assets and dead men walking.

Needing to do clear air direct capture of CO₂ increasingly looks like something we’re going to have to solve. We don’t know how to scale it. It is horrifically expensive at the moment. And we’ll need to zero nearly all emissions of greenhouse gases to make it affordable.