Chemistry Climate Working Group (CCWG)

The goal of the Chemistry Climate working group is to continue the development of the representation of chemical gas and aerosol species in the CESM and to further our understanding of the interactions between chemistry, aerosols and climate. Scientific motivations include advancing knowledge on past, present and future atmospheric composition particularly in the troposphere, interactions between atmospheric composition and the Earth System, stratosphere-troposphere coupling, aerosol direct and indirect effects on the Earth's energy balance, aerosol effects on precipitation, and impacts of global chemistry/aerosol and climate on air quality across different scales.

To achieve these research goals the CCWG maintains and develops CAM-chem, an extension of the Community Atmosphere Model (CAM). Since CAM4-chem (CESM1.1) the chemistry and aerosol schemes have been expanded to represent tropospheric composition in greater detail, coupled to comprehensive stratospheric chemistry. CAM5-chem includes the Modal Aerosol Model (MAM4). CESM2 (CAM6-chem) includes an updated tropospheric chemistry mechanism (MOZART-T1) which has expanded isoprene and terpene oxidation schemes, specific aromatic compounds (benzene, toluene, xylenes), with independent oxidation pathways. It also includes comprehensive stratospheric chemistry and interactive aerosols, similar to WACCM, to produce a reasonable atmospheric composition in the stratosphere in order to describe Stratosphere-to-Troposphere exchange processes.

CAM-chem can be run as a free-running climate model, coupled to the land model (CLM), and optionally to the ocean and ice models. It can also be run with specified dynamics (SD) using MERRA2 meteorological fields for detailed comparisons to field experiments and specific observations. The standard horizontal resolution for CAM6-chem is 1 degree, with 0.5 degree also possible.


The Chemistry Climate Working Group welcomes new users of CESM2 and CAM-chem. To help new users get started, we are developing a wiki page along with helpful guides.

We welcome suggestions for additions and improvements to it. For more information about CAM-chem see the links below:

Support Forum

Support for running CESM is available on the DiscussCESM bulletin board, where users can request assistance with science and runtime issues. The bulletin board includes a CAM-chem support forum section.

The announcements section of the forum contains guides of general use to CCWG users as well as announcements from CSEG.

Detailed instruction on how to run CESM with chemistry can be found in the Community & User Support