This manuscript is a welcome addition to the Pliocene paleoclimate literature by assessing site-specific drivers of SST change. As the authors indicate, the methodology highlights the strengths of using palaeoclimate proxy data in combination with model output to better understand the mid Piacenzian and future climate. The FCO2 methodology is novel and allows a better estimate of climate sensitivity.

The manuscript is well-written, for the most part properly referenced and the methodology is clearly explained. I have only minor suggestions for the authors to consider:

Line 25: If you are going to call the mPWP an analog provide a qualifier or brief explanation- analog means different things to different readers. Also, these are good citations to recent work, but the concept of the Pliocene as an analog began at least as far back as Budyko (1982) or Zubakov and Borzenkova (1988). There is quite a literature since then about the mPWP and its relevance to future climate.

Line 34: Haywood et al. in press should be 2024.

Line 55: The last time the top of the Mammoth subchron was dated 3.220 Ma was Cande and Kent (1995). Most of us would use 3.207 Ma. I think this might be part of the PlioVAR procedure but without explanation here it just looks like you have the wrong age. You could avoid this by cutting the sentence starting on line 53: "Geological proxy data...McClymont et al. (2020)" as it doesn't really add anything to this paper.

Line 84:  You are absolutely correct in the example of using isotope tracers rather than calculating temperature from the oxygen isotopes. However, since you are only considering SST and the Pliocene, is there a different example you could use? No one is estimating Pliocene SST using oxygen isotopes. You could, but you would need more explanation here.

Line 183: I think the PRISM3 time interval would be Dowsett et al. 2010, not 2016.

Other than these minor suggestions/comments, I like this paper and hope to see the methodology used as PlioMIP3 simulations become available.

Burton et al. applied the Fco2 method to KM5c, a crucial time period of the Pliocene targeted by the data and modeling community for intercomparison purposes. They aimed to assess the extent to which observed sea surface temperature (SST) patterns are influenced by CO2 and other forcings. The study also investigated the impact of seasonality on reconstructed mean annual changes. Additionally, site-specific calculations of equilibrium climate sensitivity (ECS) were conducted to obtain a range of Pliocene ECS values based on site location, proxy used, and the magnitude of SST changes in response to CO2 forcing.

Overall, this study presents a robust analysis using state-of-the-art data and modeling products. The manuscript is well-written, and its eventual publication in Climate of the Past is recommended. However, there are some overarching questions that the authors should address before acceptance.

The mention of "patterns of SST" in the title and throughout the manuscript raises questions about the SST pattern effect, a topic of recent interest. The authors should clarify whether the observed Pliocene warming pattern solely reflects polar amplification or is also influenced by zonal gradients or phenomena like ENSO. Recent advancements in understanding the warming patterns of other geological periods, such as the LGM, late Miocene, and PETM, could provide valuable context.

Furthermore, the manuscript may appear overly technical to readers unfamiliar with Pliocene Model Intercomparison Project (PlioMIP) terminology and concepts. It would be beneficial for the authors to articulate the fundamental questions regarding Pliocene climate change and explain how their study contributes to addressing them. The attempt to correlate data-model offsets with Fco2 may not yield significant insights, as these two factors are not inherently linked.

In addressing these points, the authors are encouraged to consider the broader implications of their findings for understanding Pliocene paleoclimate. Specifically, they should highlight how their study contributes to addressing key questions in the field and elucidating the significance of SST patterns in the Pliocene context.

Specific comments:

L85-100: While the discussions on proxy data and model simulations are pertinent, they are not directly related to the topics presented here. The authors should elaborate more on the significance of SST patterns in the broader Pliocene climate context.