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Stratospheric ozone chemistry feedbacks are not critical for the determination of climate sensitivity in CESM1(WACCM)
Author(s) -
Marsh Daniel R.,
Lamarque JeanFrançois,
Conley Andrew J.,
Polvani Lorenzo M.
Publication year - 2016
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2016gl068344
Subject(s) - stratosphere , climate sensitivity , radiative forcing , ozone layer , ozone , atmospheric sciences , atmospheric chemistry , climatology , radiative transfer , ozone depletion , environmental science , climate model , atmosphere (unit) , forcing (mathematics) , climate change , chemistry , meteorology , aerosol , physics , geology , oceanography , quantum mechanics
The Community Earth System Model‐Whole Atmosphere Community Climate Model (CESM1‐WACCM) is used to assess the importance of including chemistry feedbacks in determining the equilibrium climate sensitivity (ECS). Two 4×CO 2 model experiments were conducted: one with interactive chemistry and one with chemical constituents other than CO 2 held fixed at their preindustrial values. The ECS determined from these two experiments agrees to within 0.01 K. Similarly, the net feedback parameter agrees to within 0.01 W m −2 K −1 . This agreement occurs in spite of large changes in stratospheric ozone found in the simulation with interactive chemistry: a 30% decrease in the tropical lower stratosphere and a 40% increase in the upper stratosphere, broadly consistent with other published estimates. Off‐line radiative transfer calculations show that ozone changes alone account for the difference in radiative forcing. We conclude that at least for determining global climate sensitivity metrics, the exclusion of chemistry feedbacks is not a critical source of error in CESM.