the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Transient climate simulations of the Holocene (version 1) – experimental design and boundary conditions
- 1Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
- 2Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science & Technology, Nanjing, 210044, China
- 3State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, China Meteorological Administration, Beijing 100081, China
- 1Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
- 2Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science & Technology, Nanjing, 210044, China
- 3State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, China Meteorological Administration, Beijing 100081, China
Abstract. The Holocene, started approximately 11.5 thousand years before present (ka), is the latest interglacial period with several rapid climate changes from decades to centuries time scales superimposed on the millennium scale mean climate trend. Climate models provide useful tools to investigate the underlying dynamic mechanisms for the climate change during this well-studied time period. Thanks to the improvements of the climate model and computational power, transient simulation of the Holocene offers an opportunity to investigate the climate evolution in response to time-varying external forcings and feedbacks. Here, we present the design of a new set of transient experiments for the whole Holocene from 11.5 ka to the preindustrial period (1850 CE) (HT-11.5ka) to investigate both combined and separated effects of the main external forcing of orbital insolation, atmospheric greenhouse gas (GHG) concentrations, and ice sheets on the climate evolution over the Holocene. The HT-11.5ka simulations are performed with a relatively high-resolution version of the comprehensive Earth system model CESM1.2.1 without acceleration, both fully- and singly-forced by time-varying boundary conditions of orbital configurations, atmospheric GHGs, and ice sheets. Preliminary simulation results show a slight decrease of the global annual mean surface air temperature from 11.5 ka to 7.5 ka due to both decreases in orbital insolation and GHG concentrations, with an abrupt cooling at approximate 7.5 ka, which is followed by a continuous warming until the preindustrial period mainly due to increased GHG concentrations. The simulated cooling magnitude at 6 ka lies within the range of the 14 PMIP4 model results and is close to their median result for the mid-Holocene simulations. Further analyses on the HT-11.5ka transient simulation results will be covered by follow-up studies.
Zhiping Tian et al.
Status: closed
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RC1: 'Comment on gmd-2022-49', Anonymous Referee #1, 01 Apr 2022
Review of
"Transient climate simulations of the Holocene (version 1) – experimental design and boundary conditions"
by Zhiping Tian, Dabang Jiang, Ran Zhang, Baohuang Su
for Geoscientific Model DevelopmentThe paper describes the experimental design of a small set of transient Holocene simulations, and a few results.
Part 1.1 is a honest summary of the present knowledge of the climate evolution over the Holocene. Part 1.2 is a honest summary of the main results from previous simulations of the Holocene by different groups. Both parts are based on a good review of the present literature, and I appreciated this synthesis. They provide a good base for part 1.3 which explains clearly why new Holocene simulations, with ESMs (not EMICs), unaccelerated models, etc ... might bring new insights about the Holocene climate.
Part 2 is a very short model description. There is no need to get more in depth, as the model is fully described in the cited literature.
Part 3 describes the experimental design. The description is comprehensive, and would allow any modeller to run a similar set of experiments with its own model (or with the same model).
Part 4 gives a few preliminary results.
The paper is clear, easy to read, with a relevant structure and progression. Abstract and conclusion are fully supported by the main text. The langage seems good, but my own english does not allow me to have a relevant evaluation. I didn't find any typo. Figures are clear and readable. I thank the authors for the care taken with the manuscript.
I have no major concern about the paper, which perfectly fits the GMD category "Model experiment description paper".
I have just one minor concern.
Line 233 reads that the spin-up run has a 'stable' Atlantic Meridional Overturning Circulation (AMOC). Most (all ?) models show some variability of the AMOC on inter annual to decadal time scales. I would appreciate to get an idea of the amplitude of the inter annual to decadal variability of this experiment, particularly for the AMOC. If the amplitude is strong, the choice to start the transient experiment form a state with high or low AMOC might have some impact on the result.
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AC1: 'Reply on RC1', Zhiping Tian, 05 May 2022
We agree that models generally show some variability of the AMOC on inter annual to decadal time scales. We have drawn the time series of the AMOC strength (defined as the maximum of the mean meridional mass overturning streamfunction below 500 m north of 28°N in the Atlantic) for the 1500 years in the early Holocene spin-up experiment. Although it shows some variability on inter annual to decadal time scales, the AMOC strength is relatively stable for the last 100 years with an amplitude of approximately 25.4 Sv. This AMOC amplitude is reasonable, since it lies within the range of the 10 PMIP4 models and is comparable to the amplitude in GISS-E2-1-G and FGOAL-f3-L for the preindustrial experiments as shown in Brierley et al. (2020). The stable trends of the AMOC amplitude as well as global mean surface air and sea surface temperatures for the last 100 years in the spin-up experiment mean that the model has reached a quasi-equilibrium state as suggested by Kageyama et al. (2018). Therefore, it is reasonable to start the transient experiment from this quasi-equilibrium state. We have added the amplitude of the AMOC in the revised manuscript accordingly (Line 216).
References:
Brierley, C. M., Zhao, A., Harrison, S. P., et al.: Large-scale features and evaluation of the PMIP4-CMIP6 midHolocene simulations, Clim. Past, 16, 1847–1872, doi:10.5194/cp-16-1847-2020, 2020.
Kageyama, M., Braconnot, P., Harrison, S. P., et al.: The PMIP4 contribution to CMIP6 – Part 1: Overview and over-arching analysis plan, Geosci. Model Dev., 11, 1033–1057, doi:10.5194/gmd-11-1033-2018, 2018.
-
AC1: 'Reply on RC1', Zhiping Tian, 05 May 2022
-
RC2: 'Comment on gmd-2022-49', Anonymous Referee #2, 01 Apr 2022
Review of the paper by Zhiping Tian et al. on Transient climate simulations of the Holocene (version 1) – experimental design and boundary conditions. The paper describes a model configuration for Holocene climate using CESM1.2.1. Compared to other PMIP participants it exploits a surprisingly high resolution of ~2° in the atmosphere and 1° in the ocean and does not employ any acceleration techniques. Using this setup the authors conducted some transient runs from 11.5ka until the pre-industrial era.
I like the paper in general but feel that the authors need to add more substantial material before it can be accepted by GMD. Hence I recommend the authors to resubmit the paper after significant revision.
- The introduction leaves an impression that the authors know their topic and what they are doing. However, it consists of 3 parts and takes more than 30% of the paper. I see the authors need to make it more concise and keep only the relevant for the motivation parts.
- I agree with the first reviewer that the model description lacks some details. Which parameterisations are used in the ocean and atmosphere, which coefficients etc. all this is not there. The presented setup does not really follow the PMIP4 protocol, doesn't it? I also wonder how the ocean was initialized for the spinup?
- line 295: Is it a standard practice in PMIP? I expect the effect is enorm!
- For a GMD paper on the model setup description it would be necessary to present the model performance, scalability and throughput for different model components distinguishing between IO, ocean and atmosphere costs etc.
- My main comment is that the preliminary results are limited by one page and one plot which sounds a bit poor (10% of the paper). In the discussion of Fig.5 the authors try to interpret the drivers of Holocene climate GMST anomaly by using the additional 4 experiments where they sequentially turn off different boundary conditions. If I interpret Fig. 5 correctly I see that the anomalies in these 4 experiments do not sum to the reference experiment (HT-ALL) containing all boundary conditions. This points to the high level of nonlinearity in the system and reduces the confidence of the discussion in the results section.
- I would like to see some key diagnostics from PMIP4 and how the HT-ALL experiment aligns with the other models. As an example one could look into Chris M. Brierley 2020 (https://doi.org/10.5194/cp-16-1847-2020, 2020) and do the comparison.
- AC2: 'Reply on RC2', Zhiping Tian, 05 May 2022
Status: closed
-
RC1: 'Comment on gmd-2022-49', Anonymous Referee #1, 01 Apr 2022
Review of
"Transient climate simulations of the Holocene (version 1) – experimental design and boundary conditions"
by Zhiping Tian, Dabang Jiang, Ran Zhang, Baohuang Su
for Geoscientific Model DevelopmentThe paper describes the experimental design of a small set of transient Holocene simulations, and a few results.
Part 1.1 is a honest summary of the present knowledge of the climate evolution over the Holocene. Part 1.2 is a honest summary of the main results from previous simulations of the Holocene by different groups. Both parts are based on a good review of the present literature, and I appreciated this synthesis. They provide a good base for part 1.3 which explains clearly why new Holocene simulations, with ESMs (not EMICs), unaccelerated models, etc ... might bring new insights about the Holocene climate.
Part 2 is a very short model description. There is no need to get more in depth, as the model is fully described in the cited literature.
Part 3 describes the experimental design. The description is comprehensive, and would allow any modeller to run a similar set of experiments with its own model (or with the same model).
Part 4 gives a few preliminary results.
The paper is clear, easy to read, with a relevant structure and progression. Abstract and conclusion are fully supported by the main text. The langage seems good, but my own english does not allow me to have a relevant evaluation. I didn't find any typo. Figures are clear and readable. I thank the authors for the care taken with the manuscript.
I have no major concern about the paper, which perfectly fits the GMD category "Model experiment description paper".
I have just one minor concern.
Line 233 reads that the spin-up run has a 'stable' Atlantic Meridional Overturning Circulation (AMOC). Most (all ?) models show some variability of the AMOC on inter annual to decadal time scales. I would appreciate to get an idea of the amplitude of the inter annual to decadal variability of this experiment, particularly for the AMOC. If the amplitude is strong, the choice to start the transient experiment form a state with high or low AMOC might have some impact on the result.
-
AC1: 'Reply on RC1', Zhiping Tian, 05 May 2022
We agree that models generally show some variability of the AMOC on inter annual to decadal time scales. We have drawn the time series of the AMOC strength (defined as the maximum of the mean meridional mass overturning streamfunction below 500 m north of 28°N in the Atlantic) for the 1500 years in the early Holocene spin-up experiment. Although it shows some variability on inter annual to decadal time scales, the AMOC strength is relatively stable for the last 100 years with an amplitude of approximately 25.4 Sv. This AMOC amplitude is reasonable, since it lies within the range of the 10 PMIP4 models and is comparable to the amplitude in GISS-E2-1-G and FGOAL-f3-L for the preindustrial experiments as shown in Brierley et al. (2020). The stable trends of the AMOC amplitude as well as global mean surface air and sea surface temperatures for the last 100 years in the spin-up experiment mean that the model has reached a quasi-equilibrium state as suggested by Kageyama et al. (2018). Therefore, it is reasonable to start the transient experiment from this quasi-equilibrium state. We have added the amplitude of the AMOC in the revised manuscript accordingly (Line 216).
References:
Brierley, C. M., Zhao, A., Harrison, S. P., et al.: Large-scale features and evaluation of the PMIP4-CMIP6 midHolocene simulations, Clim. Past, 16, 1847–1872, doi:10.5194/cp-16-1847-2020, 2020.
Kageyama, M., Braconnot, P., Harrison, S. P., et al.: The PMIP4 contribution to CMIP6 – Part 1: Overview and over-arching analysis plan, Geosci. Model Dev., 11, 1033–1057, doi:10.5194/gmd-11-1033-2018, 2018.
-
AC1: 'Reply on RC1', Zhiping Tian, 05 May 2022
-
RC2: 'Comment on gmd-2022-49', Anonymous Referee #2, 01 Apr 2022
Review of the paper by Zhiping Tian et al. on Transient climate simulations of the Holocene (version 1) – experimental design and boundary conditions. The paper describes a model configuration for Holocene climate using CESM1.2.1. Compared to other PMIP participants it exploits a surprisingly high resolution of ~2° in the atmosphere and 1° in the ocean and does not employ any acceleration techniques. Using this setup the authors conducted some transient runs from 11.5ka until the pre-industrial era.
I like the paper in general but feel that the authors need to add more substantial material before it can be accepted by GMD. Hence I recommend the authors to resubmit the paper after significant revision.
- The introduction leaves an impression that the authors know their topic and what they are doing. However, it consists of 3 parts and takes more than 30% of the paper. I see the authors need to make it more concise and keep only the relevant for the motivation parts.
- I agree with the first reviewer that the model description lacks some details. Which parameterisations are used in the ocean and atmosphere, which coefficients etc. all this is not there. The presented setup does not really follow the PMIP4 protocol, doesn't it? I also wonder how the ocean was initialized for the spinup?
- line 295: Is it a standard practice in PMIP? I expect the effect is enorm!
- For a GMD paper on the model setup description it would be necessary to present the model performance, scalability and throughput for different model components distinguishing between IO, ocean and atmosphere costs etc.
- My main comment is that the preliminary results are limited by one page and one plot which sounds a bit poor (10% of the paper). In the discussion of Fig.5 the authors try to interpret the drivers of Holocene climate GMST anomaly by using the additional 4 experiments where they sequentially turn off different boundary conditions. If I interpret Fig. 5 correctly I see that the anomalies in these 4 experiments do not sum to the reference experiment (HT-ALL) containing all boundary conditions. This points to the high level of nonlinearity in the system and reduces the confidence of the discussion in the results section.
- I would like to see some key diagnostics from PMIP4 and how the HT-ALL experiment aligns with the other models. As an example one could look into Chris M. Brierley 2020 (https://doi.org/10.5194/cp-16-1847-2020, 2020) and do the comparison.
- AC2: 'Reply on RC2', Zhiping Tian, 05 May 2022
Zhiping Tian et al.
Zhiping Tian et al.
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