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: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2025-02-01
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| Series: | Earth System Dynamics |
| Online Access: | https://esd.copernicus.org/articles/16/257/2025/esd-16-257-2025.pdf |
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| Summary: | <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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| ISSN: | 2190-4979 2190-4987 |