Benchmark calculations of radiative forcing by greenhouse gases

Journal Article · Tue Nov 17 00:00:00 EST 2020 · Journal of Geophysical Research: Atmospheres

DOI:https://doi.org/10.1029/2020jd033483· OSTI ID:1721784

Pincus, Robert ^[1]; Buehler, Stefan A. ^[2]; Brath, Manfred ^[2]; Crevoisier, Cyril ^[3]; Jamil, Omar ^[4]; Evans, K. Franklin ^[5]; Manners, James ^[6]; Menzel, Raymond L. ^[7]; Mlawer, Eli J. ^[8]; Paynter, David ^[9]; Pernak, Rick L. ^[8]; Tellier, Yoann ^[3]

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1. Univ. of Colorado, Boulder, CO (United States); NOAA Physical Sciences Lab, Boulder, CO (United States); University of Colorado
2. Univ. Hamburg (Germany)
3. École Polytechnique Inst. Polytechnique de Paris, Palaiseau (France)
4. Met Office, Exeter (United Kingdom)
5. Univ. of Colorado, Boulder, CO (United States)
6. Met Office, Exeter (United Kingdom); Exeter Univ. (United Kingdom)
7. NOAA Geophysical Fluid Dynamics Lab., Princeton NJ (United States); Univ. Corporation for Atmospheric Research, Princeton, NJ (United States)
8. Atmospheric and Environmental Research, Lexington, MA (United States)
9. NOAA Geophysical Fluid Dynamics Lab., Princeton NJ (United States)

Changes in concentrations of greenhouse gases lead to changes in radiative fluxes throughout the atmosphere. The value of this change, the instantaneous radiative forcing, varies across climate models, due partly to differences in the distribution of clouds, humidity, and temperature across models, and partly due to errors introduced by approximate treatments of radiative transfer. This paper describes an experiment within the Radiative Forcing Model Intercomparision Project that uses benchmark calculations made with line–by–line models to identify parameterization error in the representation of absorption and emission by greenhouse gases. Clear–sky instantaneous forcing by greenhouse gases is computed using a set of 100 profiles, selected from a re–analysis of present–day conditions, that represent the global annual mean forcing from pre–industrial times to the present–day with sampling errors of less than 0.01 W_m^–2. Six contributing line–by–line models agree in their estimate of this forcing to within 0.025 W_m^–2 while even recently–developed parameterizations have typical errors four or more times larger, suggesting both that the samples reveal true differences among line–by–line models and that parameterization error will be readily identifiable. Agreement among line–by–line models is better in the longwave than in the shortwave where differing treatments of the water vapor vapor continuum affect estimates of forcing by carbon dioxide and methane. The impacts of clouds on instantaneous radiative forcing are estimated from climate model simulations. Here, the adjustment due to stratospheric temperature change by assuming fixed dynamical heating. Adjustments are large only for ozone and for carbon dioxide, for which stratospheric cooling introduces modest non–linearity.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States); Univ. of Colorado, Boulder, CO (United States)
• Sponsoring Organization: Centre National d'Études Spatiales; Deutsche Forschungsgemeinschaft (DFG); Thales Services; USDOE Office of Science (SC), Biological and Environmental Research (BER); USDOE Office of Science (SC), Biological and Environmental Research (BER). Earth and Environmental Systems Science Division
• Grant/Contract Number: AC02-05CH11231; SC0012399; SC0012549
• OSTI ID: 1721784
• Alternate ID(s): OSTI ID: 1770591
• Journal Information: Journal of Geophysical Research: Atmospheres, Journal Name: Journal of Geophysical Research: Atmospheres Journal Issue: 23 Vol. 125; ISSN 2169-897X
• Publisher: American Geophysical Union
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
58 GEOSCIENCES
CMIP6
RFMIP
effective radiative forcing
line by line