Journal of Meteorological Research

, Volume 33, Issue 1, pp 31–45 | Cite as

Climate Sensitivity and Feedbacks of a New Coupled Model CAMS-CSM to Idealized CO2 Forcing: A Comparison with CMIP5 Models

  • Xiaolong ChenEmail author
  • Zhun Guo
  • Tianjun Zhou
  • Jian Li
  • Xinyao Rong
  • Yufei Xin
  • Haoming Chen
  • Jingzhi Su
Special Collection on CAMS-CSM


Climate sensitivity and feedbacks are basic and important metrics to a climate system. They determine how large surface air temperature will increase under CO2 forcing ultimately, which is essential for carbon reduction policies to achieve a specific warming target. In this study, these metrics are analyzed in a climate system model newly developed by the Chinese Academy of Meteorological Sciences (CAMS-CSM) and compared with multi-model results from the Coupled Model Comparison Project phase 5 (CMIP5). Based on two idealized CO2 forcing scenarios, i.e., abruptly quadrupled CO2 and CO2 increasing 1% per year, the equilibrium climate sensitivity (ECS) and transient climate response (TCR) in CAMS-CSM are estimated to be about 2.27 and 1.88 K, respectively. The ECS is near the lower bound of CMIP5 models whereas the TCR is closer to the multi-model ensemble mean (MME) of CMIP5 due to compensation of a relatively low ocean heat uptake (OHU) efficiency. The low ECS is caused by an unusually negative climate feedback in CAMS-CSM, which is attributed to cloud shortwave feedback (λSWCL) over the tropical Indo-Pacific Ocean.

The CMIP5 ensemble shows that more negative λSWCL is related to larger increase in low-level (925–700 hPa) cloud over the tropical Indo-Pacific under warming, which can explain about 90% of λSWCL in CAMS-CSM. Static stability of planetary boundary layer in the pre-industrial simulation is a critical factor controlling the low-cloud response and λSWCL across the CMIP5 models and CAMS-CSM. Evidently, weak stability in CAMS-CSM favors lowcloud formation under warming due to increased low-level convergence and relative humidity, with the help of enhanced evaporation from the warming tropical Pacific. Consequently, cloud liquid water increases, amplifying cloud albedo, and eventually contributing to the unusually negative λSWCL and low ECS in CAMS-CSM. Moreover, the OHU may influence climate feedbacks and then the ECS by modulating regional sea surface temperature responses.

Key words

climate sensitivity climate feedback cloud shortwave feedback the Chinese Academy of Meteorological Sciences climate system model (CAMS-CSM) Coupled Model Comparison Project phase 5 (CMIP5) 


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We acknowledge the climate modeling groups (listed in Table 1) for making their model outputs available (, and the World Climate Research Program’s (WCRP’s) Working Group on Coupled Modeling (WGCM) for coordinating the CMIP5 project.


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Copyright information

© The Chinese Meteorological Society and Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  • Xiaolong Chen
    • 1
    Email author
  • Zhun Guo
    • 2
    • 1
  • Tianjun Zhou
    • 1
    • 3
  • Jian Li
    • 4
  • Xinyao Rong
    • 4
  • Yufei Xin
    • 4
  • Haoming Chen
    • 4
  • Jingzhi Su
    • 4
  1. 1.State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric PhysicsChinese Academy of SciencesBeijingChina
  2. 2.Climate Change Research Center, Institute of Atmospheric PhysicsChinese Academy of SciencesBeijingChina
  3. 3.University of the Chinese Academy of SciencesBeijingChina
  4. 4.State Key Laboratory of Severe WeatherChinese Academy of Meteorological Sciences, China Meteorological AdministrationBeijingChina

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