Fast atmosphere‐ocean model runs with large changes in CO2. Issue 21 (12th November 2013)

• Record Type: Journal Article
• Authors: Russell, Gary L.; Lacis, Andrew A.; Rind, David H.; Colose, Christopher; Opstbaum, Roger F.
• Is Part Of: Geophysical research letters. Volume 40:Issue 21(2013:Nov.)
• Page Start: 5787
• Page End: 5792
• Publication Date: 2013-11-12
• Subjects: Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/2013GL056755
• Languages: English
• ISSNs: 0094-8276

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <p>[1] How does climate sensitivity vary with the magnitude of climate forcing? This question was investigated with the use of a modified coupled atmosphere‐ocean model, whose stability was improved so that the model would accommodate large radiative forcings yet be fast enough to reach rapid equilibrium. Experiments were performed in which atmospheric CO₂ was multiplied by powers of 2, from 1/64 to 256 times the 1950 value. From 8 to 32 times, the 1950 CO₂, climate sensitivity for doubling CO₂ reaches 8°C due to increases in water vapor absorption and cloud top height and to reductions in low level cloud cover. As CO₂ amount increases further, sensitivity drops as cloud cover and planetary albedo stabilize. No water vapor‐induced runaway greenhouse caused by increased CO₂ was found for the range of CO₂ examined. With CO₂ at or below 1/8 of the 1950 value, runaway sea ice does occur as the planet cascades to a snowball Earth climate with fully ice covered oceans and global mean surface temperatures near −30°C.</p> </abstract>