It’s already bad. But when will things get so bad that it is obviously — obviously — the worst problem in the world? How long until we go over the cliff? That depends on how much we’ve heated up already, and how fast we’re getting hotter.

We have already reached dangerous levels. The heat waves throughout the northern hemisphere this summer have cost plenty, to the economy, in human suffering, ill health, even lives lost. The wildfires in California this year were much worse than they would have been without global warming. Just last year we set a new record for the total cost (adjusted for inflation) of billion-dollar climate-related disasters. They cost the U.S. over $300 billion.

As bad as it is already, extremely bad is yet to come. Some say it’ll be when total warming since pre-industrial times reaches 2°C, others say — and I agree with…