Is equilibrium climate sensitivity clouding our judgement?

Abstract
Equilibrium climate sensitivity – ECS – is easily-understood as the global mean atmospheric warming for a doubling of CO2. It is widely applied, has been studied for
over 150 years and is therefore appealing as a metric for communication of climate model
results. However, here we argue that ECS is not a good metric for comparing different
climate models and is no longer appropriate because of expanding model design and conditions. Using brief examples concerning the Pliocene epoch and the Paleocene–Eocene
Thermal Maximum, it is further posited that models which produce temperatures towards
the higher end of model intercomparisons are useful in spite of recent studies concluding
that these models are ‘too hot’. It is hoped that this brief manuscript generates discussion on how to prioritise the consideration of more useful, and potentially novel, ways of
comparing climate models going forward