“As a geologist, I think about timescales,” he went on. “The timescale of the climate system is centuries to tens of thousands of years. If we stop CO2 emissions tomorrow, which, of course, is impossible, it’s still going to warm at least for centuries, because the ocean hasn’t equilibrated. That’s just basic physics. We’re not sure how much additional warming that is, but it could easily be another seventy percent beyond what we’ve experienced. So in that sense, we’re already at 2°C. We’re going to be lucky to stop at 4°C. That’s not optimistic or pessimistic. I think that’s objective
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