Lori Sentman (NOAA GFDL): "Quantifying Equilibrium Climate Sensitivity to Atmospheric Chemistry and Composition Representations in GFDL-CM4.0 and GFDL-ESM4.1"
Rodrigo Caballero Augi (Stockholm Univ.): "Understanding polar lapse rate response in radiative-advective equilibrium"
00:38:06 delsole: This may be a silly question, but does ECS of a SOM depend on the mixed-layer depth? The convention is to use a 50 m SOM, but would the ECS change if a 10 m or 100 m SOM were used instead?
00:41:34 Jonathan Gregory: It should not make a direct difference because once eqm is reached the heat capacity is not relevant.
00:42:40 Gavin Schmidt: The GISS models had both non-interactive and interactive composition versions in CMIP6 - but the differences in ECS were small (0.1-0.3ºC) - discussed in Kelley et al (2020) for instance.
00:42:43 Jonathan Gregory: C dT/dt = F - alpha T (alpha>0 climate feedback parameter) gives the same T=F/alpha regardless of F at eqm
00:42:52 Nadir Jeevanjee: I would guess that changes to slab depth would primarily affect the timescale for equilibration, but not the equilibrated state itself
00:42:54 Jonathan Gregory: regardless of C, sorry
00:42:58 William Ingram: I'd expect 10m to mess up the timing of the seasonal cycle enough that cloud feedbacks might be affected
00:43:52 Jonathan Gregory: Yes, the seasonal cycle could have an effect, but the heat convergence is tuned make it match the intended climatology, so it should be the same
00:44:32 William Ingram: Sorry, yes, the anomalous seasonal cycle!
00:46:59 Lori Sentman: I agree that the slab depth would mainly impact the timescale of response as it damps the perturbation.
00:47:36 Clare Singer: Replying to "The GISS models had ..."
Re: this point. I’m wondering how much we trust the strength of these 5 negative feedbacks. Can we constrain them independently? Clearly in the GFDL ESM they are large. Maybe they are much smaller in the GISS model? Or there is some compensating positive feedback?
00:55:51 Gavin Schmidt: Replying to "The GISS models had ..."
happy to try and coordinate a more detailed comparison!
01:02:33 Lori Sentman: Replying to "The GISS models ha..."
This is an interesting comparison result. I'd be interested in discussing this further.
01:08:35 Eric DeWeaver: Are there any implications for sea ice decline? I think that would matter for surface energy balance.
01:09:30 Brian Rose: Can you recap the weakened surface radiator fin argument? Is this mostly about the narrowing of the spectral window?