Numerical modeling is an important way to study the evolution mechanism of whole Earth spheres and its prediction of future climate status provides science advice to policy makers.

However, the processes closely related to carbon cycle, such as ecology and terrestrial marine biogeochemistry, are not taken into consideration in the traditional climate system model. It is urgent to develop an Earth system model (ESM), which includes processes such as aerosols, atmospheric chemistry, dynamic vegetation, biogeochemistry and carbon/nitrogen cycle. 

Recently, a study published in Journal of Advances in Modeling Earth Systems (JAMES) introduced the second version of CAS-ESM. "CAS-ESM2.0 is the first ESM developed independently by Chinese scientists," said Dr. ZHANG He from the Institute of Atmospheric Physics (IAP) of the Chinese Academy of Sciences, the first author of the study.

There are now 8 component models in the CAS-ESM2.0, including atmospheric model IAP AGCM5.0, ocean model LICOM2, land model CoLM, ice model CICE4, aerosols and atmospheric chemistry model IAP AACM, dynamic vegetation model IAP DGVM, land biogeochemistry model embedded within the CoLM land model, and ocean biogeochemistry model IAP OBGCM.

The processes of marine and land biogeochemical, dynamic vegetation, fire, and atmospheric chemistry, that are closely related to carbon cycle and ecological process, are considered in the CAS-ESM2.0. Therefore, instead of being prescribed in traditional climate system model, the future carbon dioxide concentration can be predicted in CAS-ESM2.0. In addition to global simulation, CAS-ESM2.0 also includes a regional component model (WRF), which can couple with the global model and provide the refined simulation of regional climate. 

CAS-ESM (Image by IAP)

"CAS-ESM2.0 can reasonably simulate the meridional heat transport of the atmosphere and ocean, along with the vertical distribution of the Atlantic Meridional Overturning Circulation (AMOC). The climatological features of ocean temperature, salinity and sea ice density are well captured by CAS-ESM2.0," said ZHANG.

In addition to the study published in JAMES, the data description articles of CAS-ESM2.0 have also been published in the CMIP6 special issue in Advances in Atmospheric Sciences.  

"This is just a good start and we still have a long way to go. There are 23 MIPs in CMIP6, and we will continue to complete other experiments and share the simulation results with scientists around the world. In addition, we need to further improve the performance of the model," said ZHANG.