The tendency of climate models to overstate warming in the tropical
troposphere has long been noted. Here we examine individual runs from 38
newly-released Coupled Model Intercomparison Project version 6 (CMIP6)
models and show that the warm bias is now observable globally as well.
We compare CMIP6 runs against observational series drawn from
satellites, weather balloons and reanalysis products. We focus on the
1979-2014 interval, the maximum span for which all observational
products are available and for which models were run using
historically-observed forcings. For lower- and mid-troposphere layers
both globally and in the tropics, all 38 models overpredict warming in
every target observational analogue, in most cases significantly so, and
the average differences between models and observations are
statistically significant. We present evidence that consistency with
observed warming would require lower model Equilibrium Climate
Sensitivity (ECS) values.