Carbon budgets for 1.5 and 2 °C targets lowered by natural wetland and permafrost feedbacks

• Published in: Nature Geoscience
• Main Authors: Comyn-Platt, E, Hayman, G, Huntingford, C, Chadburn, SE, Burke, EJ, Harper, AB, Collins, WJ, Webber, CP, Powell, T, Cox, PM, Gedney, N, Sitch, S
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer Nature 2018
• Subjects: permafrost
• Online Access: http://hdl.handle.net/10871/34441; https://doi.org/10.1038/s41561-018-0174-9

This is the author accepted manuscript. The final version is available from Springer Nature via the DOI in this record Data availability: The data that support the findings of this study are available from the corresponding author upon request. Code availability: JULES is an open-source model and the code branch used in this work is available from the Met Office science repository using the following URL (registration required): https://code.metoffice.gov.uk/trac/jules/browser/main/branches/dev/edwardcomynplatt/vn4.8_1P5_DEGREES?rev=11764. The author correction to this article is in ORE: http://hdl.handle.net/10871/36073. Please follow the DOI in that record to go to the corrected version of the article in Nature Geoscience Global methane emissions from natural wetlands and carbon release from permafrost thaw have a positive feedback on climate, yet are not represented in most state-of-the-art climate models. Furthermore, a fraction of the thawed permafrost carbon is released as methane, enhancing the combined feedback strength. We present simulations with an inverted intermediate complexity climate model, which follows prescribed global warming pathways to stabilization at 1.5 or 2.0 °C above pre-industrial levels by the year 2100, and which incorporates a state-of-the-art global land surface model with updated descriptions of wetland and permafrost carbon release. We demonstrate that the climate feedbacks from those two processes are substantial. Specifically, permissible anthropogenic fossil fuel CO2emission budgets are reduced by 17–23% (47–56 GtC) for stabilization at 1.5 °C, and 9–13% (52–57 GtC) for 2.0 °C stabilization. In our simulations these feedback processes respond more quickly at temperatures below 1.5 °C, and the differences between the 1.5 and 2 °C targets are disproportionately small. This key finding holds for transient emission pathways to 2100 and does not account for longer-term implications of these feedback processes. We conclude that natural feedback processes from wetlands and ...