And I can't state this enough: Our estimates of high climate sensitivity are based on the best estimates of available observations. There is a high probability (from a risk perspective) that climate sensitivity is even higher than our seemingly 'higher' (than e.g. IPCC's +3°C for 2xCO₂) estimates.
Exactly the same logic applies to climate sensitivity. We need to work on the assumption that Dr James Hansen et al is correct with their higher climate sensitivity models because we won’t know if mainstream climate science is completely wrong about low climate sensitivity until it is too late.