EARTH
In the literature: partially resolved
Can paleoclimate evidence rule out climate sensitivity above 5 K?
In plain words
Several recent climate models warm by more than 5 degrees for doubled CO2. Past climates such as the last ice age may show this is too much.
Precise statement
Determine whether combined constraints from the Last Glacial Maximum, the mid-Pliocene, the early Eocene and the historical record exclude $\mathrm{ECS} > 5\ \mathrm{K}$ at the 95 percent level, accounting for state dependence of feedbacks and forcing uncertainties. An answer is a posterior probability for $\mathrm{ECS} > 5\ \mathrm{K}$ with stated assumptions.
What would settle it
Bayesian synthesis of paleoclimate proxies and model emergent constraints with explicit state-dependence and structural uncertainty.
Related problems
- Special case of What is Earth's equilibrium climate sensitivity?