Anthropogenic changes of interannual-to-decadal climate variability in CMIP6 multi-ensemble simulations

Arthur Coquereau aLaboratoire d’Océanographie Physique et Spatiale, Univ Brest CNRS IRD Ifremer, Brest, France

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Florian Sévellec aLaboratoire d’Océanographie Physique et Spatiale, Univ Brest CNRS IRD Ifremer, Brest, France
bODYSSEY Project-Team, INRIA CNRS, Brest, France

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Thierry Huck aLaboratoire d’Océanographie Physique et Spatiale, Univ Brest CNRS IRD Ifremer, Brest, France

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Joël J.-M. Hirschi cMarine Systems Modelling, National Oceanography Centre, Southampton, SO14 3ZH, UK

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Antoine Hochet aLaboratoire d’Océanographie Physique et Spatiale, Univ Brest CNRS IRD Ifremer, Brest, France

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Abstract

As well as having an impact on the background state of the climate, global warming due to human activities could affect its natural oscillations and internal variability. In this study, we use four initial-condition ensembles from the CMIP6 framework to investigate the potential evolution of internal climate variability under different warming pathways for the 21st century. Our results suggest significant changes in natural climate variability, and point to two distinct regimes driving these changes. First, a decrease of internal variability of surface air temperature at high latitudes and all frequencies, associated with a poleward shift and the gradual disappearance of sea-ice edges, which we show to be an important component of internal variability. Second, an intensification of the interannual variability of surface air temperature and precipitation at low latitudes, which appears to be associated with the El Niño–Southern Oscillation (ENSO). This second regime is particularly alarming because it may contribute to making the climate more unstable and less predictable, with a significant impact on human societies and ecosystems.

© 2024 American Meteorological Society. This is an Author Accepted Manuscript distributed under the terms of the default AMS reuse license. For information regarding reuse and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Arthur Coquereau, arthur.coquereau@univ-brest.fr

Abstract

As well as having an impact on the background state of the climate, global warming due to human activities could affect its natural oscillations and internal variability. In this study, we use four initial-condition ensembles from the CMIP6 framework to investigate the potential evolution of internal climate variability under different warming pathways for the 21st century. Our results suggest significant changes in natural climate variability, and point to two distinct regimes driving these changes. First, a decrease of internal variability of surface air temperature at high latitudes and all frequencies, associated with a poleward shift and the gradual disappearance of sea-ice edges, which we show to be an important component of internal variability. Second, an intensification of the interannual variability of surface air temperature and precipitation at low latitudes, which appears to be associated with the El Niño–Southern Oscillation (ENSO). This second regime is particularly alarming because it may contribute to making the climate more unstable and less predictable, with a significant impact on human societies and ecosystems.

© 2024 American Meteorological Society. This is an Author Accepted Manuscript distributed under the terms of the default AMS reuse license. For information regarding reuse and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Arthur Coquereau, arthur.coquereau@univ-brest.fr
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