Carbon cycle and climate feedbacks under CO<sub>2</sub> and non-CO<sub>2</sub> overshoot pathways

<p>Reducing emissions of non-carbon dioxide (<span class="inline-formula">CO<sub>2</sub></span>) greenhouse gases (GHGs), such as methane (<span class="inline-formula">CH<sub>4</sub></span>) and nitrous oxide (<span class=&...

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Main Authors: I. Melnikova, P. Ciais, K. Tanaka, H. Shiogama, K. Tachiiri, T. Yokohata, O. Boucher
Format: Article
Language:English
Published: Copernicus Publications 2025-02-01
Series:Earth System Dynamics
Online Access:https://esd.copernicus.org/articles/16/257/2025/esd-16-257-2025.pdf
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author I. Melnikova
I. Melnikova
P. Ciais
K. Tanaka
K. Tanaka
H. Shiogama
K. Tachiiri
K. Tachiiri
T. Yokohata
O. Boucher
author_facet I. Melnikova
I. Melnikova
P. Ciais
K. Tanaka
K. Tanaka
H. Shiogama
K. Tachiiri
K. Tachiiri
T. Yokohata
O. Boucher
author_sort I. Melnikova
collection DOAJ
description <p>Reducing emissions of non-carbon dioxide (<span class="inline-formula">CO<sub>2</sub></span>) greenhouse gases (GHGs), such as methane (<span class="inline-formula">CH<sub>4</sub></span>) and nitrous oxide (<span class="inline-formula">N<sub>2</sub>O</span>), complements <span class="inline-formula">CO<sub>2</sub></span> mitigation in limiting global warming. However, estimating carbon–climate feedback for these gases remains fraught with uncertainties, especially under overshoot scenarios. This study investigates the impact of <span class="inline-formula">CO<sub>2</sub></span> and non-<span class="inline-formula">CO<sub>2</sub></span> gases with nearly equal levels of effective radiative forcing on the climate and carbon cycle, using the Earth system model (ESM) IPSL-CM6A-LR. We first present a method to recalibrate methane and nitrous oxide concentrations to align with published radiative forcings, ensuring accurate model performance. Next, we carry out a series of idealised ramp-up and ramp-down concentration-driven experiments and show that, while the impacts of increasing and decreasing <span class="inline-formula">CO<sub>2</sub></span> and non-<span class="inline-formula">CO<sub>2</sub></span> gases on the surface climate are nearly equivalent (when their radiative forcing magnitudes are set to be the same), regional differences emerge. We further explore the carbon cycle feedbacks and demonstrate that they differ under <span class="inline-formula">CO<sub>2</sub></span> and non-<span class="inline-formula">CO<sub>2</sub></span> forcing. <span class="inline-formula">CO<sub>2</sub></span> forcing leads to both carbon–climate and carbon–concentration feedbacks, whereas non-<span class="inline-formula">CO<sub>2</sub></span> gases give rise to the carbon–climate feedback only. We introduce a framework, building on previous studies that addressed <span class="inline-formula">CO<sub>2</sub></span> forcing, to separate the carbon–climate feedback into a temperature term and a temperature–<span class="inline-formula">CO<sub>2</sub></span> cross-term. Our findings reveal that these feedback terms are comparable in magnitude for the global ocean. This underscores the importance of considering both terms in carbon cycle feedback framework and climate change mitigation strategies.</p>
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spelling doaj-art-d87d555c2c824162bc5a1fd86c2724482025-02-06T10:59:20ZengCopernicus PublicationsEarth System Dynamics2190-49792190-49872025-02-011625727310.5194/esd-16-257-2025Carbon cycle and climate feedbacks under CO<sub>2</sub> and non-CO<sub>2</sub> overshoot pathwaysI. Melnikova0I. Melnikova1P. Ciais2K. Tanaka3K. Tanaka4H. Shiogama5K. Tachiiri6K. Tachiiri7T. Yokohata8O. Boucher9Earth System Division, National Institute for Environmental Studies (NIES), Tsukuba, 305-8506, JapanLaboratoire des Sciences du Climat et de l'Environnement (LSCE), IPSL, CEA/CNRS/UVSQ, Université Paris-Saclay, Gif-sur-Yvette, 91191, FranceLaboratoire des Sciences du Climat et de l'Environnement (LSCE), IPSL, CEA/CNRS/UVSQ, Université Paris-Saclay, Gif-sur-Yvette, 91191, FranceEarth System Division, National Institute for Environmental Studies (NIES), Tsukuba, 305-8506, JapanLaboratoire des Sciences du Climat et de l'Environnement (LSCE), IPSL, CEA/CNRS/UVSQ, Université Paris-Saclay, Gif-sur-Yvette, 91191, FranceEarth System Division, National Institute for Environmental Studies (NIES), Tsukuba, 305-8506, JapanEarth System Division, National Institute for Environmental Studies (NIES), Tsukuba, 305-8506, JapanResearch Institute for Global Change, Japan Agency for Marine-Earth Science and Technology, Yokohama, 236-0001, JapanEarth System Division, National Institute for Environmental Studies (NIES), Tsukuba, 305-8506, JapanInstitut Pierre-Simon Laplace, Sorbonne Université/CNRS, Paris, 75005, France<p>Reducing emissions of non-carbon dioxide (<span class="inline-formula">CO<sub>2</sub></span>) greenhouse gases (GHGs), such as methane (<span class="inline-formula">CH<sub>4</sub></span>) and nitrous oxide (<span class="inline-formula">N<sub>2</sub>O</span>), complements <span class="inline-formula">CO<sub>2</sub></span> mitigation in limiting global warming. However, estimating carbon–climate feedback for these gases remains fraught with uncertainties, especially under overshoot scenarios. This study investigates the impact of <span class="inline-formula">CO<sub>2</sub></span> and non-<span class="inline-formula">CO<sub>2</sub></span> gases with nearly equal levels of effective radiative forcing on the climate and carbon cycle, using the Earth system model (ESM) IPSL-CM6A-LR. We first present a method to recalibrate methane and nitrous oxide concentrations to align with published radiative forcings, ensuring accurate model performance. Next, we carry out a series of idealised ramp-up and ramp-down concentration-driven experiments and show that, while the impacts of increasing and decreasing <span class="inline-formula">CO<sub>2</sub></span> and non-<span class="inline-formula">CO<sub>2</sub></span> gases on the surface climate are nearly equivalent (when their radiative forcing magnitudes are set to be the same), regional differences emerge. We further explore the carbon cycle feedbacks and demonstrate that they differ under <span class="inline-formula">CO<sub>2</sub></span> and non-<span class="inline-formula">CO<sub>2</sub></span> forcing. <span class="inline-formula">CO<sub>2</sub></span> forcing leads to both carbon–climate and carbon–concentration feedbacks, whereas non-<span class="inline-formula">CO<sub>2</sub></span> gases give rise to the carbon–climate feedback only. We introduce a framework, building on previous studies that addressed <span class="inline-formula">CO<sub>2</sub></span> forcing, to separate the carbon–climate feedback into a temperature term and a temperature–<span class="inline-formula">CO<sub>2</sub></span> cross-term. Our findings reveal that these feedback terms are comparable in magnitude for the global ocean. This underscores the importance of considering both terms in carbon cycle feedback framework and climate change mitigation strategies.</p>https://esd.copernicus.org/articles/16/257/2025/esd-16-257-2025.pdf
spellingShingle I. Melnikova
I. Melnikova
P. Ciais
K. Tanaka
K. Tanaka
H. Shiogama
K. Tachiiri
K. Tachiiri
T. Yokohata
O. Boucher
Carbon cycle and climate feedbacks under CO<sub>2</sub> and non-CO<sub>2</sub> overshoot pathways
Earth System Dynamics
title Carbon cycle and climate feedbacks under CO<sub>2</sub> and non-CO<sub>2</sub> overshoot pathways
title_full Carbon cycle and climate feedbacks under CO<sub>2</sub> and non-CO<sub>2</sub> overshoot pathways
title_fullStr Carbon cycle and climate feedbacks under CO<sub>2</sub> and non-CO<sub>2</sub> overshoot pathways
title_full_unstemmed Carbon cycle and climate feedbacks under CO<sub>2</sub> and non-CO<sub>2</sub> overshoot pathways
title_short Carbon cycle and climate feedbacks under CO<sub>2</sub> and non-CO<sub>2</sub> overshoot pathways
title_sort carbon cycle and climate feedbacks under co sub 2 sub and non co sub 2 sub overshoot pathways
url https://esd.copernicus.org/articles/16/257/2025/esd-16-257-2025.pdf
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