Clara Deser (NCAR): "Southern Ocean SST impacts on the Tropics in CESM1 and CESM2"
Jonah Bloch-Johnson (Univ. of Reading): "A simple model of nonlinear radiative feedbacks"
00:35:09 Jiang Zhu: Hi Jonah, Thanks for the great talk. Do you expect the polynomial fit has large model dependence? Can we use that (from HadCM) to predict CESM results?
00:36:10 Bosong Zhang: Nice talk Jonah! Regarding the uniform feedback, any explanation why it appears as a second order term?
00:36:11 Kyle Armour: Thanks, Jonah. Have you looked at your framework of a polynomial fit in the context of individual feedbacks? That is, does this work equally well for clouds, water vapor, etc, or does it work better for some feedbacks and worse for others?
00:38:03 Kyle Armour: Thanks!
00:41:03 Gavin Schmidt: Also different in HadSST5...
00:47:56 Gavin Schmidt: Does the sea ice respond to the PACE’d SST or to the ocean model generated ocean temperatures?
00:55:53 Ceppi, Paulo A: Do we have any sense as to which of the forcing datasets is more realistic? Presumably the difference comes from aerosols?
00:57:06 Chris Holloway: It is interesting that SOPACE1 has much stronger cooling in the Labrador Sea region. Links to AMOC?
00:58:06 Gavin Schmidt: There is a specific issue with the biomass burning BC in CMIP6 that caused a spurious warming in CESM2 (Fasullo et al, 2022).
00:58:21 Chris Bretherton: Are the imposed Southern Ocean (SO) SST anomalies larger than the internal variability of the CESM1 and CESM2 ensembles? How far out of energy balance is the SO itself in these simulations (i. e. are the imposed SST perturbations inconsistent with the underlying coupled model)?
00:58:28 Dave Bonan: Thanks for the interesting talk, Clara! Have you performed pacemaker experiments with smaller Southern Ocean domains? Yue Dong has a nice paper (Dong et al., 2022, J. Clim.) showing the impact of Southern Ocean cooling on global SST trends is sensitive to the longitudinal location of forcing in the Southern Ocean.
01:02:04 Ian Eisenman: Thanks for a great talk! Thinking about your results with Jonah's talk (and also Dave Bonan's comment) in mind, would you expect Pacemaker simulations like this to linearly add up? What I mean is, if you separated the global surface area outside the tropics into a set of regions/patches and then did Pacemaker simulations in each region (i.e., nudging SST in each region to match observations), would you expect the anomalous tropical SST from all of these simulations to add up to the observed topical SST? If they aren't expected to linearly add up, in what sense does the result of a Pacemaker simulation that nudges SST in a single region (the Southern Ocean) imply that this region is *driving* changes in tropical SST?
01:02:17 Karsten Haustein (he/him): Any guess what’s causing the larger SST low cloud feedback in CESM2 (SOPACE2 for that matter)? Changes in cloud microphysics?
01:04:12 Isaac Held: Is there a significant change in ENSO statistics in either model?
01:05:05 Kyle Armour: Thanks, Clara. Could you say more about what has changed between the forcing datasets? Gavin mentioned biomass burning was an issue. But what has caused such a big change in the pattern of warming in the CESM2 experiments (run with old vs new forcings)? Relatedly, are the ERFs available for both forcing datasets? It would be interesting to look at the historical feedbacks and Effective Climate Sensitivities (EffCS) values in those two CESM2 ensembles. I suspect they will be different from one another, and different from ECS.
01:15:09 Kyle Armour: Thanks, Clara!