Reduced global fire activity due to human demography slows global warming by enhanced land carbon uptake

Wu, Chao; Sitch, Stephen; Huntingford, Chris ORCID: https://orcid.org/0000-0002-5941-7770; Mercado, Lina M. ORCID: https://orcid.org/0000-0003-4069-0838; Venevsky, Sergey; Lasslop, Gitta; Archibald, Sally; Staver, A. Carla. 2022 Reduced global fire activity due to human demography slows global warming by enhanced land carbon uptake. Proceedings of the National Academy of Sciences, 119 (20), e2101186119. 12, pp. 10.1073/pnas.2101186119

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Abstract/Summary

Fire is an important climate-driven disturbance in terrestrial ecosystems, also modulated by human ignitions or fire suppression. Changes in fire emissions can feed back on the global carbon cycle, but whether the trajectories of changing fire activity will exacerbate or attenuate climate change is poorly understood. Here, we quantify fire dynamics under historical and future climate and human demography using a coupled global climate–fire–carbon cycle model that emulates 34 individual Earth system models (ESMs). Results are compared with counterfactual worlds, one with a constant preindustrial fire regime and another without fire. Although uncertainty in projected fire effects is large and depends on ESM, socioeconomic trajectory, and emissions scenario, we find that changes in human demography tend to suppress global fire activity, keeping more carbon within terrestrial ecosystems and attenuating warming. Globally, changes in fire have acted to warm climate throughout most of the 20th century. However, recent and predicted future reductions in fire activity may reverse this, enhancing land carbon uptake and corresponding to offsetting ∼5 to 10 y of global CO2 emissions at today’s levels. This potentially reduces warming by up to 0.11 °C by 2100. We show that climate–carbon cycle feedbacks, as caused by changing fire regimes, are most effective at slowing global warming under lower emission scenarios. Our study highlights that ignitions and active and passive fire suppression can be as important in driving future fire regimes as changes in climate, although with some risk of more extreme fires regionally and with implications for other ecosystem functions in fire-dependent ecosystems.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1073/pnas.2101186119
UKCEH and CEH Sections/Science Areas:	Hydro-climate Risks (Science Area 2017-)
ISSN:	0027-8424
Additional Information. Not used in RCUK Gateway to Research.:	Open Access paper - full text available via Official URL link.
NORA Subject Terms:	Meteorology and Climatology
Date made live:	20 Oct 2022 15:05 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/533391

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