The AR6 SPM and Technical Summary are both now available for download. I'm pulling down the latter and will see what it might have to say about clouds*.
* Besides: "they're puffy and white and sometimes they look like bunnies and sometimes they look like dragons"
From Pg 41: Magnitude of climate system response: In this Report, it has been possible to reduce the long-standing uncertainty ranges for metrics that quantify the response of the climate system to radiative forcing, such as the equilibrium climate sensitivity (ECS) and the transient climate response (TCR), due to substantial advances (e.g.,
a 50% reduction in the uncertainty range of cloud feedbacks) and improved integration of multiple lines of evidence, including paleoclimate information.
Pg 42: Effects of short-lived climate forcers on global warming: The AR5 assessed the radiative forcing for emitted compounds.
The AR6 has extended this by assessing the emissions-based ERFs also accounting for aerosol–cloud interactions. The best estimates of ERF attributed to sulphur dioxide (SO2) and CH4 emissions are substantially greater than in AR5, while that of black carbon is substantially reduced. The magnitude of uncertainty in the ERF due to black carbon emissions has also been reduced relative to AR5. (Section TS.3.1)
Pg 49:
Some CMIP6 models demonstrate an improvement in how clouds are represented. CMIP5 models commonly displayed a negative shortwave cloud radiative effect that was too weak in the present climate. These errors have been reduced, especially over the Southern Ocean, due to a more realistic simulation of supercooled liquid droplets with sufficient numbers and an associated increase in the cloud optical depth. Because a negative cloud optical depth feedback in response to surface warming results from ‘brightening’ of clouds via active phase change from ice to liquid cloud particles (increasing their shortwave cloud radiative effect), the extratropical cloud shortwave feedback in CMIP6 models tends to be less negative, leading to a better agreement with observational estimates (medium confidence). CMIP6 models generally represent more processes that drive aerosol–cloud interactions than the previous generation of climate models, but there is only medium confidence that those enhancements improve their fitness-for-purpose of simulating radiative forcing of aerosol–cloud interactions. {6.4, 7.4.2, FAQ 7.2}
Pg 49: Two important quantities used to estimate how the climate system responds to changes in greenhouse gas (GHG) concentrations are the equilibrium climate sensitivity (ECS) and transient climate response (TCR16). The CMIP6 ensemble has broader ranges of ECS and TCR values than CMIP5 (see Section TS.3.2 for the assessed range).
These higher sensitivity values can, in some models, be traced to changes in extratropical cloud feedbacks (medium confidence). To combine evidence from CMIP6 models and independent assessments of ECS and TCR, various emulators are used throughout the report. Emulators are a broad class of simple climate models or statistical methods that reproduce the behaviour of complex ESMs to represent key characteristics of the climate system, such as global surface temperature and sea level projections. The main application of emulators in AR6 is to extrapolate insights from ESMs and observational constraints to produce projections from a larger set of emissions scenarios, which is achieved due to their computational efficiency. These emulated projections are also used for scenario classification in WGIII. {Box 4.1, 4.3.4, 7.4.2, 7.5.6, Cross-Chapter Box 7.1, FAQ 7.2}
That's enough for this purpose. Certainly clouds are addressed in AR6 and mainstream science's knowledge of how clouds figure into all this is certainly improving. One thing I always find when I go to the the assessment reports is how far beyond the typical USMB conversation are the work of actual scientists. These excerpts are from introductory texts in a technical summary. This is about the simplest level of material you'll find in The Physical Science Basis outside the summary for policymakers but we both know that most posters here can't follow one word in ten from those documents. Why do you listen to those people Todd?
