If you run in the right circles, you might encounter someone who breathlessly tells us that the downward trend in estimates of climate sensitivity (how much added warmth comes from added atmospheric CO2) got turned around by a new study in Nature Climate Change, and we’re back to a best estimate of Equilibrium Climate Sensitivity (ECS) of 3.0 for doubled CO2.

That would indeed appear to be a plausible interpretation of the study. But the study itself is badly flawed, as climate sensitivity expert Nic Lewis demonstrates in a critique. Read the whole critique for the details, but here’s the conclusion:

Marvel et al.’s calculations of TCR and ECS estimates for the three observational studies cited contain multiple errors. They are also conceptually wrong in the case of Otto et al. 2013, since the underlying forcing estimates used in that study already reflect efficacies.

The methodological deficiencies in and multiple errors made by Marvel et al., the disagreements of some of its forcing estimates with those given elsewhere for the same model, and the conflicts between the Marvel et al. findings and those by others—most notably by James Hansen using the previous GISS model, mean that its conclusions have no credibility.