For a doubling of CO2 the equilibrium climate sensitivity (ECS) is from 1.5 C to 4.5 C with 66% confidence. – AR5
For a doubling of CO2 the transient climate sensitivity (TCS) is from 1.0 C to 3.0 C with 90% confidence. – AR4
I just noticed the X to 3X in both ranges. Why is the intermediate in the same ratio as the equilibrium? Is this the climate iron ratio? No.
From here to there the bounds are kind of the same, but more tightly constrained on the way to there. So we could have a hockey stick with a blade near the end. So when we are about to get there, as things settle down, we can get a dramatic up or down turn. That’s my kind of equilibrium.
Expert assessments. That’s what we have.