Sure. It was started in 2017, when the UN environment program put up that first declaration that no matter how fast or how slow we reduce our emissions, negative emissions technologies will be needed. At that time, they said it was sometime by mid-century. We now know it's sooner, because we haven't been reducing our emissions, which is essential. We have to ensure that our emissions are reduced, whether it's through efficiency, as just discussed, or through direct reduction of greenhouse gases into the atmosphere.
There's no question that's needed, but of course now we know from scientific research that the negative emissions technologies are needed. We're seeing it. A paper that came out last week updated the tipping points. Even at just slightly greater than 1°C, we're going to start seeing these major tipping points in the climate system.