The graph below shows the relationship between downwelling longwave radiation in the tropics (i.e. the greenhouse effect) and atmospheric CO2. I used RRTM_LW as the radiative transfer model, which is the model used by NCAR.
TROPICAL ATMOSPHERE ADJUSTED TO RIDGEWAY’S GLA MODEL
As you can see, CO2 is a very minor component of the greenhouse effect in the tropics, and almost all of its effect is in the first 20 PPM CO2. Once you get above 100 PPM CO2, adding more CO2 has almost no effect. Water vapor completely dominates, and other gases are almost irrelevant. An increase from 50 PPM to 1,000 PPM CO2 only increases downwelling longwave radiation by 1%.
The same model is used by the following organizations, and can be downloaded from this link : RRTM/RRTMG
RRTMG Global and Regional Model Applications
- ECMWF (European Centre for Medium-Range Weather Forecasts), Reading, UK
- Integrated Forecast System (IFS), ERA40 Reanalysis
Began operational use of LW on 27 June 2000 (version prior to LW_v2.0),
Began operational use of LW and SW with McICA on 5 June 2007,
Upgrade to v4.84 in progress as of April 2010
- MPI (Max Planck Institute), Hamburg, Germany
- ECHAM5
Began operational use of LW in 2002 (prior to LW_v2.0 from ECMWF),
Upgrade to v4.84 in progress as of April 2010
- NCEP (National Centers for Environmental Prediction)
- Global Forecast System (GFS)
Began operational use of RRTMG_LW at 12Z on 28 August 2003,
Began operational use of RRTMG_SW at 12Z on 27 July 2010
- NCEP (National Centers for Environmental Prediction)
- Climate Forecast System (CFS)
Began operational use of LW in 2004,
Update to include SW and newer LW expected in September 2010
- NCEP (National Centers for Environmental Prediction)
- Rapid Update Cycle Forecast Model (RUC)
Began operational use of LW in November 2008 (prior to LW_v2.0)
- NCAR (National Center for Atmospheric Research)
- Weather Research and Forecasting Model (WRF-ARW)
Released as LW and SW radiation option in WRF_v3.1 in April 2009
- NCAR (National Center for Atmospheric Research)
- Community Atmosphere Model (CAM5) and
Community Earth System Model (CESM1, formerly CCSM)
CAM5 and CESM1 released with RRTMG/McICA (LW and SW) on 25 June 2010
- NASA/GSFC (Goddard Space Flight Center)
- Goddard Earth Observing System (GEOS-5) Data Assimilation System
Implementation and testing of LW_v4.83 and SW_v3.8 began in 2009
- LMD (Laboratory for Dynamical Meteorology), France
- LMDZ climate model
Began operational use of LW in 2008-09 (prior to LW_v2.0 from ECMWF).
- CMA (China Meteorological Administration), China
- Global/Regional Assimilation and Prediction System (GRAPES)
Implementation and testing of LW_v4.71 and SW_v3.8 began in February 2009
- Meteo-France (French National Meteorological Service), France
- Meso-NH (Non-hydrostatic Meso-scale atmospheric model)
Included LW as radiation option in 2009 (prior to LW_v2.0 from ECMWF).
RRTM/RRTMG Copyright and Disclaimer
Copyright © 2002-2010, Atmospheric and Environmental Research, Inc. (AER, Inc.). This software may be used, copied, or redistributed as long as it is not sold and this copyright notice is reproduced on each copy made. This model is provided as is without any express or implied warranties.
