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Cited by 72Atmospheric aerosols and cloudsClimate variability and modelsGeology and Paleoclimatology Research

Clouds and the Faint Young Sun Paradox

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Goldblatt, C., Zahnle, K. J.·2011·Climate of the Past
DOI 10.5194/cp-7-203-2011

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Abstract

Abstract. We investigate the role which clouds could play in resolving the Faint Young Sun Paradox (FYSP). Lower solar luminosity in the past means that less energy was absorbed on Earth (a forcing of −50 W m−2 during the late Archean), but geological evidence points to the Earth having been at least as warm as it is today, with only very occasional glaciations. We perform radiative calculations on a single global mean atmospheric column. We select a nominal set of three layered, randomly overlapping clouds, which are both consistent with observed cloud climatologies and reproduced the observed global mean energy budget of Earth. By varying the fraction, thickness, height and particle size of these clouds we conduct a wide exploration of how changed clouds could affect climate, thus constraining how clouds could contribute to resolving the FYSP. Low clouds reflect sunlight but have little greenhouse effect. Removing them entirely gives a forcing of +25 W m−2 whilst more modest reduction in their efficacy gives a forcing of +10 to +15 W m−2. For high clouds, the greenhouse effect dominates. It is possible to generate +50 W m−2 forcing from enhancing these, but this requires making them 3.5 times thicker and 14 K colder than the standard high cloud in our nominal set and expanding their coverage to 100% of the sky. Such changes are not credible. More plausible changes would generate no more than +15 W m−2 forcing. Thus neither fewer low clouds nor more high clouds can provide enough forcing to resolve the FYSP. Decreased surface albedo can contribute no more than +5 W m−2 forcing. Some models which have been applied to the FYSP do not include clouds at all. These overestimate the forcing due to increased CO2 by 20 to 25% when pCO2 is 0.01 to 0.1 bar.

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  • No plausible combination of few low clouds and many high, icy clouds solves the FYS problem.

    “However, no plausible combination of few low clouds (which tend to reflect sunlight) and many high, icy clouds (which tend to warm the surface with downwelling infrared) solves the FYS problem (211).”

    From The Archean atmosphere (2020) · cites this paper as [211]

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Research works printed but not linked: 2

  1. Curry, J. A. and Webster, P. J.: Thermodynamics of the Atmo- spheres and Ocean, Academic Press, London, 471 pp., 1999.
  2. Forster, P., Ramaswamy, V., Artaxo, P., Berntsen, T., Betts, R., Fa- hey, D., Haywood, J., Lean, J., Lowe, D., Myhre, G., Nganga, J., Prinn, R., Raga, G., Schulz, M., and Van Dorland, R.: Changes in Atmospheric Constituents and in Radiative Forcing, in: Cli- mate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Inter- governmental Panel on Climate Change, edited by: Solomon, S., Qin, D., Manning, M., Chen, Z., Marquis, M., Averyt, K., Tig- nor, M., and Miller, H. L., Cambridge Univ. Press, Cantab. UK and New York, NY, USA, 2007.

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Authors
Goldblatt, C., & Zahnle, K. J.
Affiliations
Ames Research Center (US)
Venue
Climate of the Past
Publisher
Copernicus GmbH
Published
2011-03-04
Volume
7
Issue
1
Pages
203-220
ISSN
  • 1814-9324 (ISSN-L)
  • 1814-9332
DOI
10.5194/cp-7-203-2011
OpenAlex
W2139299573
Cited by
71
References
78
Citations by year
2026: 1 · 2025: 4 · 2024: 2 · 2023: 5 · 2022: 2 · 2021: 4 · 2020: 4 · 2019: 3 · 2018: 5 · 2017: 5 · 2016: 6 · 2015: 3 · 2014: 4 · 2013: 12 · 2012: 4
FWCI
6.84
Type
journal article
Language
en
Open access
Licence
Locations
  • Climate of the past (publishedVersion, cc-by)
  • arXiv (Cornell University) (submittedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
  • UVic’s Research and Learning Repository (University of Victoria) (submittedVersion)
  • arXiv (Cornell University)
Funders
  • National Aeronautics and Space Administration
  • NASA Astrobiology Institute
Topics
  • Physical Sciences › Environmental Science › Global and Planetary Change › Atmospheric aerosols and clouds
  • Physical Sciences › Environmental Science › Global and Planetary Change › Climate variability and models
  • Physical Sciences › Earth and Planetary Sciences › Atmospheric Science › Geology and Paleoclimatology Research
Keywords
faint young Sun paradox, clouds, cloud radiative forcing, low-level clouds, high clouds, greenhouse effect, surface albedo, early Earth climate, CO2 forcing

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