Text S1.

MISR Simulator Base State Climatology
This section of the supplement is dedicated to understanding how the mean cloud climatology or base state of the models differs from observations. Here and in later analysis, the MISR output is averaged over 5 latitude bands: Tropics -20° to 20°, Subtropics ±20° to ±40°, and Midlatitudes ±40° to ±60°. The mean CTH-OD histogram observed by MISR, along with simulated histograms for CESM2 and IPSL SSP 585 simulations are shown in Figures S1 and S2 . All three histograms are averages taken over the period 2001 to 2015, which is the portion of the SSP 585 simulation that is based on historical emissions (rather than projected emissions) that overlaps with the MISR record. The MISR observations are restricted to ocean, and the model averages are restricted to ocean to match.
Figure S1 shows that distribution of clouds in CESM2 and IPSL differ noticeably between each other and with the observations. Of particular note is that IPSL does not produce much mid-level cloud (between 5 and 7 km), which have a cooling effect on the tropical climate (Bourgeois et al., 2016), and produces more optically thin high clouds (OD less than 3.6) than is observed by MISR. In contrast, CESM2 has more mid-level clouds and has more high cloud with optical depths between 1.3 and 23 than observations. In both models high clouds are predominantly located between 11 and 13 kilometers (in agreement with observations), but the observed distribution is wider, with more cloud occurring outside of the 11-13 km bin, than the models (especially IPSL). The thin distribution of IPSL has implication for our WCTH that are discussed below.
The histograms averaged over the subtropics and midlatitudes are shown in Figure S2 . Total cloud occurrence in the subtropics (20o to 40o) is dominated by low clouds, with much less high and mid-level clouds as compared to the tropics. High clouds are lower in altitude and optically thinner on average than in the tropics. The most occupied vertical bin is between 9 and 11 km in the Norther Hemisphere (NH) and 7 to 9 km in the Southern Hemisphere (SH). In both models and observations there are fewer optically thin clouds above 5 km in the SH than in the NH.
In the midlatitudes the cloud patterns are dominated by midlatitude cyclones. Optically thick high clouds occur lower in the atmosphere than in the subtropics or tropics in both observations and models. The presence of a mid-level cloud peak remains visible in the MISR observations and CESM2 simulations, located in the 3 to 4 km height bin. In IPSL, high clouds are optically thicker than observations, with a significant fraction of high clouds having optical depth greater than 60.
Bourgeois, Q., Ekman, A. M. L., Igel, M. R., & Krejci, R. (2016). Ubiquity and impact of thin mid-level clouds in the tropics.Nature Communications , 7 (1), 1–6. https://doi.org/10.1038/ncomms12432