Why the Forcing from Carbon Dioxide Scales as the Logarithm of Its Concentration

Journal Article · Fri Jul 01 00:00:00 UTC 2022 · Journal of Climate

DOI: https://doi.org/10.1175/JCLI-D-21-0275.1 · OSTI ID:1870739

Romps, David M. ^[1]; Seeley, Jacob T. ^[2]; Edman, Jacob P. ^[3]

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1. a Department of Earth and Planetary Science, University of California, Berkeley, California, b Climate and Ecosystem Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California
2. c Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts
3. d KoBold Metals, Berkeley, California

Abstract The radiative forcing from carbon dioxide is approximately logarithmic in its concentration, producing about 4 W m ⁻² of global-mean forcing for each doubling. Although these are basic facts of climate science, competing explanations for them have been given in the literature. Here, the reasons for the logarithmic forcing of carbon dioxide are explored in detail and a simplified model for the forcing is constructed. An essential component is the particular distribution of absorption coefficients within the 15- μ m band of carbon dioxide. An alternative explanation, which does not depend on the spectrum of carbon dioxide but instead hinges on the tropospheric lapse rate, is shown to be neither necessary nor sufficient to explain the logarithmic forcing of carbon dioxide and to be generally inapplicable to well-mixed greenhouse gases in Earth’s atmosphere.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Atmospheric Radiation Measurement (ARM) Data Center
• Sponsoring Organization: USDOE; USDOE Office of Science (SC), Biological and Environmental Research (BER)
• Grant/Contract Number: AC02-05CH11231
• OSTI ID: 1870739
• Journal Information: Journal of Climate, Journal Name: Journal of Climate Journal Issue: 13 Vol. 35; ISSN 0894-8755
• Publisher: American Meteorological SocietyCopyright Statement
• Country of Publication: United States
• Language: English