Non-Monotonic Response of the Climate System to Abrupt CO2 Forcing

We explore the climate system response to abrupt CO2 forcing, spanning the range 1 × to 8×CO2, with two state-of-the-art coupled atmosphere-ocean-sea-ice-land models: the NASA Goddard Institute for Space Studies Model E2.1-G (GISS-E2.1-G) and the Community Earth System Model (CESM-LE). We find that...

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Bibliographic Details
Published in:Geophysical research letters 2021-03, Vol.48 (6), p.n/a
Main Authors: Mitevski, Ivan, Orbe, Clara, Chemke, Rei, Nazarenko, Larissa, Polvani, Lorenzo M.
Format: Article
Language:English
Subjects:
AMOC
Atlantic Meridional Overturning Circulation (AMOC)
Atmosphere
Atmospheric models
Carbon dioxide
Carbon dioxide atmospheric concentrations
Carbon dioxide concentration
Climate
Climate change
Climate models
Climate sensitivity
Climate system
Dynamics
ECS
Evaporation
Ice
Meteorology And Climatology
non‐monotonic response
Northern Hemisphere
Ocean dynamics
Ocean models
Oceans
Precipitation
sea‐ice
Sensitivity
Surface temperature
tropical width
Warm water
Water circulation
Water temperature
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Summary:We explore the climate system response to abrupt CO2 forcing, spanning the range 1 × to 8×CO2, with two state-of-the-art coupled atmosphere-ocean-sea-ice-land models: the NASA Goddard Institute for Space Studies Model E2.1-G (GISS-E2.1-G) and the Community Earth System Model (CESM-LE). We find that the effective climate sensitivity is a non-monotonic function of CO2 in both models, reaching a minimum at 3×CO2 for GISS-E2.1-G, and 4×CO2 for CESM-LE. A similar non-monotonic response is found in Northern Hemisphere surface temperature, sea-ice, precipitation, the latitude of zero precipitation minus-evaporation, and the strength of the Hadley cell. Interestingly, the Atlantic meridional overturning circulation collapses when non-monotonicity appears and does not recover for larger CO2 forcings. Analyzing the climate response over the same CO2 range with slab ocean versions of the same models, we demonstrate that the climate system's non-monotonic response is linked to ocean dynamics.
ISSN:0094-8276
1944-8007
DOI:10.1029/2020GL090861