Bosong Zhang (Princeton/GFDL) "Exploring the SST pattern effect on climate feedback and climate sensitivity in GFDL models"
Jing Feng (Princeton/GFDL) "How a stable Longwave feedback is maintained under global warming?"
Dennis Hartmann (Univ. of Washington) "The Antarctic ozone hole and the pattern effect on climate sensitivity"
09:19:09 From Jonah Bloch-Johnson : @bosong - it’s interesting that forcing the extratropical in an atmosphere-only experiment has a modest impact, but a big impact when the atmosphere and ocean are coupled. is there a way to measure how much adding in the coupling increases the impact of a perturbation in a given region?
09:22:27 From Xianglei Huang : @bosong just a technical question, for your solar radiation experiment, how did you make the change, say, just scale the incoming solar spectra irradiance at all wavelengths with the same proportionality? As atmospheric absorption/surface reflectance of visible and near-IR radiations are quite different, I could easily see a “spatial pattern effect” of visible forcing change different from that of near-IR forcing change. Have you try to separate them? Thanks.
09:26:16 From chris colose : @bosong has anyone extended your type of experiment to seasonal forcing in addition to the spatial structure? I have in mind getting closer to Milankovitch-style forcing & assessing the different feedbacks involved even the global mean is ~0
09:26:20 From Marc Alessi (he/him) : @Bosong: I think I misunderstood this part of the talk, but for the GF reconstruction, did you just take the SST output from the coupled model (after the radiative perturbation was applied) and then convolve it with the GF? I am surprised the GF reconstructions for the SO +/- 4 Wm^-2 scenarios matched the coupled model… The GF has basically no magnitude in the SO, so even if a significant change in SST is realized here, I wouldn’t expect much of a change in the global mean of whatever response variable you’re looking at. I.e., I would not have expected the GF to be able to reproduce what the coupled model did here
09:28:02 From Bosong Zhang : @Jonah Thanks for your question. My understanding is that the tropics is more effective in damping external forcing, as the GF shows large radiative cooling when the SST warming is added over the WP. The SO is less effective in damping the forcing. When forcing is added over the SO, it induces large warming.
09:30:18 From Bosong Zhang : @Xianglei. Thanks for your question. Yes, I think we did this over all wavelengths using the same proportionality. That is a good point. Although we have not considered the wavelength dependence in this project, future studies should explore more on this issue.
09:32:12 From Bosong Zhang : @chris. Thanks. I am not aware of this. I know that previous studies have addressed variations in obliquity, which has zero global mean change in incoming solar radiation.
09:35:00 From Bosong Zhang : @Marc. Thanks for your questions. Yes, I am also surprised that the GF is pretty effective here. I am using the A=1.5K 30 year experiments without any significance test. If you include significance test, like removing the so-called “noises”, the GF would underestimate the responses. So the GF reconstruction does involve some caveats. Its more like a qualitative analysis than a quantitative one.
09:36:45 From Nadir Jeevanjee : Jake Seeley’s 2020 GRL emphasizes the role of interaction between moist adiabatic warming and feedback in the CO2 band
09:36:51 From Andrew Williams (he/him) : @bosong, does the GF work better for the solar *reduction* experiments when you use cooling patches instead of A=+1.5K?
09:36:59 From Nadir Jeevanjee : @ Tim’s question
09:38:53 From Nadir Jeevanjee : Haha
09:39:29 From Dessler, Andrew E : Dennis: it’s not too late to be a postdoc at GFDL. I’m sure someone there would hire you.
09:40:21 From Bosong Zhang : @Andrew, that’s a good point. I expect it is the case but have not tried that yet. I will give it a try. Thanks!
09:40:32 From Zhihong Tan : @Marc the results are not inconsistent. The SO solar perturbation experiments lead to large tropical SST changes (more than that from tropical solar perturbation), so convolved with the SST green’s function will lead to significant TOA radiation (and other) responses.
09:53:15 From Gavin Schmidt : The biggest issue here though is that models have included the ozone hole and have simulated the southern winds shift for decades, and yet do not respond in the tropical Pacific in the way shown. Neither do they produce southern ocean cooling in the long term (Polvani etc.). What is your reasoning for why?
09:55:44 From Gavin Schmidt : FWIW, the response to winds is quite distinct from the response to anomalous freshwater from the melting ice-sheets/shelves.
09:57:24 From Clare Singer (she/her) : I thought you were looking at October to March (aka encompassing DJF)?
09:58:59 From Gavin Schmidt : Oct-Mar was the season looked at even back in Miller et al 2006.
10:00:09 From Tim Merlis : The annual-mean direct response to CO2 (ERF) is positive SAM too (Menzel & Merlis, 2019)
10:01:01 From Nadir Jeevanjee : Thanks all. Great forum.