The speakers were:
Timothy Myers (Univ. of Wyoming): "Same Cloud Change, Different Radiative Impact: Lessons from a Perturbed Parameter Ensemble"
Gregory Cesana (Columbia/NASA Goddard): "A Reconciled Satellite Record Reveals a Negative Low Cloud Feedback Over the Past 47 Years"
Tapio Schneider (Caltech): "High-resolution Simulations Reveal Positive Global Warming Feedback from Pacific Low Clouds"
2026-11-10 09:09:33 From Marcus van Lier-Walqui (he/him) to Everyone:
these have covarying impacts, or covariance is accounted for?
2026-11-10 09:14:49 From Marcus van Lier-Walqui (he/him) to Everyone:
Replying to "these have covarying impacts, or covariance is acc...":
slide 2 or 3
2026-11-10 09:15:53 From XIA LI to Everyone:
Replying to "these have covarying impacts, or covariance is acc...":
✅
2026-11-10 09:20:34 From Michael Diamond to Everyone:
Tim: Do you have a sense of why the response to advection in particular is not captured? Does that need higher resolution to get at Sc-Cu transition mechanisms?
2026-11-10 09:23:40 From Timothy A Myers to Everyone:
Replying to "Tim: Do you have a sense of why the response to ad...":
It’s very unclear to me why there is this deficiency. The Sc to Cu transition may be key as you suggest. Lagrangian analysis would be helpful.
2026-11-10 09:24:17 From Andrew Williams to Everyone:
Replying to "Tim: Do you have a sense of why the response to ad...":
I wonder if anyone has looked at the CCFs in a coupled km-scale model? These runs exist now, it would be a nice test
Michael Diamond, Alex Gonzalez, Clare Singer:👍
2026-11-10 09:26:20 From Gavin Schmidt to Everyone:
An increase in satellite LCC might be a response to a change in high or mid level clouds that were masking LCC, can we rule that out?
Tianle Yuan:👍
2026-11-10 09:26:53 From Florent Brient to Everyone:
Replying to "Tim: Do you have a sense of why the response to ad...":
Indeed, you may be interested by H. Lewis works on Lagrangian analysis. One of them: doi.org/10.1029/2025GL116330
Timothy A Myers:👍
2026-11-10 09:27:31 From Timothy A Myers to Everyone:
Replying to "Tim: Do you have a sense of why the response to ad...":
@Andrew Williams I don’t think so. Nice idea.
2026-11-10 09:27:47 From Tianle Yuan to Everyone:
Replying to "An increase in satellite LCC might be a response t...":
It would be great to have some info on how these different products are splined into a uniform record.
2026-11-10 09:28:01 From Paquita Zuidema to Everyone:
Cloud optical depth must be decreasing then? Or cloud morphology becoming more variable?
2026-11-10 09:31:14 From Michael Diamond to Everyone:
Greg: How much of an issue is observing over different parts of the diurnal cycle based on which satellite(s) are available at a given time? Also, how are you getting CASCCAD values before the CloudSat/CALIPSO era?
2026-11-10 09:31:16 From Mark Zelinka to Everyone:
Replying to "An increase in satellite LCC might be a response t...":
@Gavin: Indeed. Obscuration effects have been accounted for and removed in this analysis. A riveting paper from 2025 discussed how this is done in practice and the implications for high vs low cloud feedbacks and adjustments: https://acp.copernicus.org/articles/25/1477/2025/
Tianle Yuan, Gavin Schmidt:👍
Andrew Williams:😃
2026-11-10 09:33:20 From Clara Deser to Everyone:
Replying to "An increase in satellite LCC might be a response t...":
Nice talk! It would be nice to separate the forced vs. internal components of the observed historical SSTs used in the AMIP simulations.
Tianle Yuan:👍
2026-11-10 09:33:53 From Clare Singer to Everyone:
@Greg - this seems like a pattern effect and definition problem of using local T vs global T to define the low cloud feedback. Does this work suggest to you that maybe using global-mean T is more confusing or less useful when comparing between historical changes and future projections?
Leif, Andrew Williams:👍
2026-11-10 09:34:02 From Timothy A Myers to Everyone:
Replying to "An increase in satellite LCC might be a response t...":
@Mark Zelinka that 2025 paper is riveting and fascinating!
Clare Singer, Michael Diamond:😂
2026-11-10 09:36:52 From Paquita Zuidema to Everyone:
In surface observations from Barbados/Caribbean, we see an increase in the CL=8 category: clouds with bases at 2 levels, this is cumulus with thin overlying stratiform cloud near the inversion. Eastman et al 2025 JGR . this seems consistent w warmer SSTs and a more stable troposphere (and Greg’s work) but it would be good to generalize.
2026-11-10 09:38:37 From Clara Deser to Everyone:
We have two papers under review on this topic. I’d be happy to share them with everyone once we’ve received the reviews. - Clara
XIA LI:👍
2026-11-10 09:39:08 From Andrew Williams to Everyone:
The ForceSMIP paper that I’m aware of is here: https://iacweb.ethz.ch/staff/rjnglin/papers/2026_Wills_etal_ForceSMIP.pdf
@Gavin Schmidt
2026-11-10 09:40:51 From Greg Cesana to Everyone:
Replying to "Greg: How much of an issue is observing over diffe...":
Good question. We used CASCCAD in the CCF method to derive the Sc and Cu components, and then we used another method based on tropical average of cloud fraction to derive Sc Cu components in the satellite datasets. This method was built using CASCCAD (described in other papers).
2026-11-10 09:42:37 From Greg Cesana to Everyone:
Replying to "An increase in satellite LCC might be a response t...":
I didn’t have time to describe into detail, but we use omega500 to screen out regimes with high clouds. However, we find similar results when using all regimes.
2026-11-10 09:50:19 From Ceppi, Paulo A to Everyone:
Tapio, do your cloud adjustments agree with the CMIP range?
2026-11-10 09:51:00 From Florian Tornow to Everyone:
I'm surprised that drizzle/rain had no role in the response (opposite to Tim's presentation). Could that be connected to the aerosol configuration?
2026-11-10 09:55:17 From Clare Singer to Everyone:
Replying to "Tapio, do your cloud adjustments agree with the CM...":
I think this “adjustment” is maybe somewhat different from how it’s computed with amip runs, because any land-ocean warming contrasts that impose what we categorize as “adjustments” in GCMs would not be captured by this local framework, right?
2026-11-10 09:57:14 From Steve Klein to Everyone:
Tapio, have you quantified whether the mean state cloud and radiation produced by the LES agrees with observations? This is relevant in light of Tim’s talk today.
Tianle Yuan, Clare Singer:👍
2026-11-10 09:59:14 From Andrew Williams to Everyone:
thanks all!
2026-11-10 09:59:20 From Florent Brient to Everyone:
Thanks for the talks