"Years ago some people ran models to predict the effect of aerosols—sulfur, basically—being injected into the atmosphere from different parts of the world. What happens if we do it from Europe? North America? China? India? The outcomes were surprisingly different. It really matters where you do it. And it then affects each part of the world differently. But if I had to place a bet right here, right now, in this pub, based on what I’ve seen, I’d say it’s going to come down to China versus India."