23rd Century surprises: Long-term dynamics of the climate and carbon cycle under both high and net negative emissions scenarios

17996 8 97721 2 300909 document 97721 esd-2021-23.pdf application/pdf 567724b4a381ab5eb212bb397ed32deb MD5 16462667 2022-05-10 11:28:35 https://pure.iiasa.ac.at/id/eprint/17996/1/esd-2021-23.pdf 17996 1 1 application/pdf text en public cc_by_4

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http://eprints.org/relation/isVersionOf https://pure.iiasa.ac.at/id/document/97721 http://eprints.org/relation/isVolatileVersionOf https://pure.iiasa.ac.at/id/document/97721 http://eprints.org/relation/issmallThumbnailVersionOf https://pure.iiasa.ac.at/id/document/97721 archive 353 disk0/00/01/79/96 2022-05-10 11:31:34 2025-03-12 05:01:01 2022-05-10 11:31:34 article show 1 Koven C. Arora V. Cadule P. Fisher R. Jones C. Lawrence D. Lewis J. 2344 0000-0002-8155-8924 Lindsey K. Mathesius S. Meinshausen M. Mills M. Nicholls Z. 2343 0000-0002-4767-2723 Sanderson B. Swart N. Wieder W. Zickfeld K. 23rd Century surprises: Long-term dynamics of the climate and carbon cycle under both high and net negative emissions scenarios submitted ECE Future climate projections from Earth system models (ESMs) typically focus on the timescale of this century. We use a set of four ESMs and one Earth system model of intermediate complexity (EMIC) to explore the dynamics of the Earth’s climate and carbon cycles under contrasting emissions trajectories beyond this century, to the year 2300. The trajectories include a very high emissions, unmitigated fossil-fuel driven scenario, as well as a second mitigation scenario that diverges from the first scenario after 2040 and features an “overshoot”, followed by stabilization of atmospheric CO2 concentrations by means of large net-negative CO2 emissions. In both scenarios, and for all models considered here, the terrestrial system switches from being a net sink to either a neutral state or a net source of carbon, though for different reasons and centered in different geographic regions, depending on both the model and the scenario. The ocean carbon system remains a sink, albeit weakened by climate-carbon feedbacks, in all models under the high emissions scenario, and switches from sink to source in the overshoot scenario. The global mean temperature anomaly generally follows the trajectories of cumulative carbon emissions, except that 23rd-century warming continues after the cessation of carbon emissions in several models, both in the high emissions scenario and in one model in the overshoot scenario. While ocean carbon cycle responses qualitatively agree both in globally integrated and zonal-mean dynamics in both scenarios, the land models qualitatively disagree in zonal-mean dynamics, in the relative roles of vegetation and soil in driving C fluxes, in the response of the sink to CO2, and in the timing of the sink-source transition, particularly in the high emissions scenario. The lack of agreement among land models on the mechanisms and geographic patterns of carbon cycle feedbacks, alongside the potential for lagged physical climate dynamics to cause warming long after CO2 concentrations have stabilized, point to the possibility of surprises in the climate system beyond the 21st century time horizon, even under relatively mitigated global warming scenarios, which should be taken into consideration when setting global climate policy. 2022-04-22 published Copernicus 10.5194/esd-2021-23 3374 3377 public Earth System Dynamics TRUE 2190-4987 23rd Century surprises: Long-term dynamics of the climate and carbon cycle under both high and net negative emissions scenarios no info:eu-repo/semantics/article