Peer review of: Emergent constraints on future projections of the western North Pacific Subtropical High (2020)


RR2
REVIEWER COMMENTS second round Reviewer #2 (Remarks to the Author):
L32: Change “those in the simple” to “suggested by the” L44: change “remain” to “remaining”
  2nd Review of manuscript #NCOMMS-19-3009875A entitled “Emergent constraints on future
 projections of the western North Pacific Subtropical High”
 The authors have done a good job of addressing my primary concerns. The resulting manuscript is
 much improved and fit for publication. I especially appreciate the added robustness associated
 with the hierarchical statistical framework, the new figures, and the more complete investigation of
 physical mechanisms driving the emergent relationship. I only have some brief technical
 corrections at this time.
   L53: Remove “there are” since this is only two of many persistent biases in GCMs. “Two well-
 known chronic biases in current climate models are a cold tongue ...”
 L66: Add a citation when mentioning emergent constraints here (e.g., Hall et al 2019;
 https://www.nature.com/articles/s41558-019-0436-6)
 L206-209: Breakup into two sentences after “systematic model biases”. A second sentence along
 these lines would be appropriate: “This constraint suggests a reduction in the CMIP5 intermodel
 variance by about 45% and is supported by sound physical mechanisms.”
 Reviewer #3 (Remarks to the Author):
 PAPER NUMBER: NCOMMS-19-3009875A
 JOURNAL: Nature Communications
 TITLE: Emergent constraints on future projections of the western North Pacific Subtropical High
 The authors have effectively responded to my previous comments and the manuscript has been
 much improved. However, some parts of the manuscript are still difficult to read, and it lacks some
 important details. I think it will likely be publishable after further revisions.
 1. Please add more detailed information on the methodology used in the present study. Some of
 the detailed comments are as follows.
 - Line 87: Please specify the season of SST patterns (I guess it’s summer, right?)
 - Lines 111-114: I think the methodology to define T1 and T2 should be understandable for
 readers in sufficient detail without reading the method section. It would be much better to add
 more detailed explanation here.
 - Line 161-162: The method how to derive Fig. 5a is still unclear. Please add more detailed
 explanation. Does the “related” mean the projection of future SST changes (i.e., rcp85 run –
 historical run) onto PC1 or PC2?
 - Lines 257: I guess observational SST dataset is not included to define T1 or T2. If I’m right, the
 sentence is misleading. If I’m wrong, a more detailed description on how to define T1 and T1
 indices is still needed.
 2. The physical interpretation from Fig. 6a to Fig 6e needs to be more clear. There seems to be a
 logical jump in Fig 6e. How does the historical SW-SST feedback relate to future WP SST warming?
 In particular, the SST warming center associated with PC1 appears in 120E-180E (Fig. 5a), but the
 region for SW-SST feedback is located further east. Is there any physical explanation for that?
 3. The linkage between SW-cloud feedback and GMST also needs to be strengthened. Particularly,

 given that future surface warming pattern shown in Fig. 5b is quite different from cloud fraction
 pattern shown in Fig. 1d, a more detailed mechanism how the local marine stratocumulus can
 change global mean SST should be added. I think the mechanism section is important to justify
 the emergent constraint method used in the present study, thus author needs to elaborate on it.
 A few more comments are as follows:
 Line 173: precipitation heating  convective heating
 Line 175: Gill response  Gill-type response
 Line 255: Does the ‘absolute SST’ means ‘area-averaged SST’?
 Line 261-263: I think the author should choose either subtracting the mean tropical SST or just
 using original SST when defining T1 and T2. The low correlation coefficient between PC2 and T2
 when using original SST cannot justify the methodology and it gives an impression that the
 method used in this study is arbitrary.