GISS-GC is an NSF and NASA-funded project that couples the NASA Goddard Institute for Spaces Studies (GISS) ModelE general circulation model with the GEOS-Chem chemical transport model. The goal of GISS-GC is to facilitate the study of climate-chemistry interactions across Earth's history and into its future.

There are three configurations of GISS-GC in development:

Global Change and Air Pollution (GCAP)

GCAP is especially designed for studying the impact of future climate change on atmospheric composition and surface air quality. Meteorology is archived from the version of the GISS GCM frozen for the CMIP6 simulations. We provide meteorology at and since the preindustrial and for several future scenarios ranging from extreme mitigation to extreme warming. Users may also generate their own meteorology for driving GEOS-Chem. The current version is GCAP 2.0, which is described by Murray et al. (2021).

ICE age Chemistry and Proxies (ICECAP)

ICECAP is designed for studying atmospheric chemistry in paleo climates with significantly different land covers and for interpreting ice-core records and other proxy data. Archived GISS meteorology is first used to drive a dynamic global vegetation model (LPJ-LMfire) to generate consistent land cover products. We will provide a variety of products from the PMIP experiments. The original version of ICECAP is described by Murray et al. (2014).

GC online in E2.1

ModelE2.1 itself includes an optional online reduced atmospheric chemistry mechanism (see Kelley et al., 2020). For those who wish to study two-way chemistry-climate interactions with the more complex GEOS-Chem mechanism, or use a consistent chemical mechanism with sister projects (e.g., CESM2-GC) to isolate how uncertainties in climate propagate to uncertainties in composition, we are implementing GEOS-Chem as an alternative online chemical mechanism within E2.1. Currently in beta testing.

Ongoing Projects

GISS-GC users around the world
Click on each location to learn more about how GISS-GC is being used to study atmospheric chemistry-climate interactions. Please e-mail Lee Murray to add your project to the map!

Using GCAP

Obtaining GCAP 2.0 source code

GCAP 2.0 entered the GEOS-Chem standard code in version 13.1. You can follow the standard directions for downloading the model.

git clone https://github.com/geoschem/GCClassic.git ./Code.GCAP2
cd Code.GCAP2
git submodule update --init --recursive

Note that submodules always download in a headless state. If you wish to track your changes, you will need to check out or create a branch.

Generating run directories

You can create run directories just like in regular GEOS-Chem!

Downloading meteorology and emission files

GCAP 2.0 is compatable with the new python data downloader for downloading input files.

Just point download_data.py to the GISS-GC repository

python3 download_data.py dryrun.log --ur

The following table summarizes the meteorology presently available for download from the GISS-GC server.

ScenarioVariant Label1851-1860 C.E.2001-2014 C.E.2040-2049 C.E.2090-2099 C.E.
ScenarioVariant Label1851-1860 C.E.2001-2014 C.E.2040-2049 C.E.2090-2099 C.E.
Historical (Nudged to MERRA-2)🌏
SSP1-1.9 (Extreme Mitigation)r1i1p1f2🌍🌎
SSP4-3.4 (Paris Agreement)r1i1p1f2🌎🌏
SSP5-8.5 (Extreme Warming)r1i1p1f2🌍🌎

Additional scenarios and variants can be generated by email request to Lee Murray.


Downloading meteorology and emission files

The following table summarizes the ICECAP meteorology presently available for download from the GISS-GC server.

Scenario∆Ts (oC)Years AvailableTopographyOrbital ForcingSSTsCO2 (ppmv)CH4 (ppbv)N2O (ppbv)
Scenario∆Ts (oC)Years AvailableTopographyOrbital ForcingSSTsCO2 (ppmv)CH4 (ppbv)N2O (ppbv)
Present Day (PD)0.06Modern-0.05 ka (2000 C.E.)CMIP63691778316
Preindustrial (PI)-0.76Modern0.1 ka (1850 C.E.)CMIP6284808273
Mid-Holocene (MH)-0.66Modern6 kaPMIP4264597262
Last Glacial Maximum (LGM)-4.76LICC21 kaPMIP4188375200
Last Glacial Maximum (LGM2) -5.76LICC21 kaAssimilated188375200
Last Interglacial (LIG)-0.46Modern127 kaPMIP4275685255

Additional scenarios can be generated by email request to Lee Murray.

Getting Help

GISS-GC Google Group

The GISS-GC Google Group (giss-gc@googlegroups.com) is a place for GISS-GC users to ask questions and exchange experiences about using GCAP, ICECAP and/or GC online within E2.1.

To join the Google Group, please sign into your Google account and search for GISS-GC and click 'Ask to join'.

Your group membership should be processed by the group managers shortly.

You may also find the GEOS-Chem Chemistry-Ecosystem-Climate Working Group email list useful.

Contact Information

Please contact Lee Murray with any questions or to report any issues.