Preprints
https://doi.org/10.5194/egusphere-2025-4000
https://doi.org/10.5194/egusphere-2025-4000
29 Sep 2025
 | 29 Sep 2025
Status: this preprint is open for discussion and under review for Earth System Dynamics (ESD).

Ocean dynamics amplify remote warming effects of reforestation

Pierre Etienne Banville, Alexander J. MacIsaac, and Kirsten Zickfeld

Abstract. Forestation, including reforestation, afforestation, and forest restoration, is prevalent in net-zero climate strategies due to the large carbon sequestration potential of forests. In addition to capturing carbon, forestation has biogeophysical effects that can influence surface temperatures locally (local effects), and at distant locations (non-local effects). Biogeophysical effects may offset the cooling benefits of carbon sequestration, hence requiring a robust understanding of their mechanisms to adequately integrate forestation into climate mitigation strategies. Yet, the role of ocean dynamics, such as ocean circulation, ocean-atmosphere interactions, and ocean-sea ice interactions in mediating the non-local effects of forestation remains underexplored. In this study, we investigate the impact of ocean dynamics on the magnitude and geographic patterns of the non-local biogeophysical effects of large-scale reforestation, with the exclusion of cloud feedbacks, over a multi-century timescale using the University of Victoria Earth System Climate Model. We conduct multi-century paired global reforestation simulations, with the first set of simulations using a dynamic ocean and the second set using prescribed sea surface temperatures. We separate local from non-local effects using the checkerboard approach. Our results show that non-local warming effects are of much greater magnitude and encompass a greater geographic area, particularly at high latitudes, when ocean dynamics are considered. Moreover, this study shows that ocean dynamics introduce a lag in the non-local effects, leading to a continued increase in non-local warming even after the local effects have stabilized. This committed non-local warming is driven by the thermal inertia of the ocean, which sustains a gradual long-term increase in sea surface temperatures, combined with amplifying climate feedbacks. Decision-making frameworks must therefore consider the complete Earth system response to forestation over a sufficiently long timeframe to account for the committed non-local warming.

Competing interests: Kirsten Zickfeld is an editor for this journal.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.
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Pierre Etienne Banville, Alexander J. MacIsaac, and Kirsten Zickfeld

Status: open (until 10 Nov 2025)

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Pierre Etienne Banville, Alexander J. MacIsaac, and Kirsten Zickfeld
Pierre Etienne Banville, Alexander J. MacIsaac, and Kirsten Zickfeld

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Short summary
Reforestation can help fight climate change by absorbing carbon, but it also affects temperatures locally and remotely through complex interactions with the atmosphere and oceans. Using a climate model, we found that the non-carbon physical effects of forests on climate can cause warming in distant locations that strengthens over centuries, amplified by oceanic processes. These results show that long-term, Earth-wide effects must be considered when planning forest-based climate solutions.
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