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https://doi.org/10.5194/bg-2019-492
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2019-492
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 20 Jan 2020

Submitted as: research article | 20 Jan 2020

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This preprint is currently under review for the journal BG.

Is there warming in the pipeline? A multi-model analysis of the zero emission commitment from CO2

Andrew H. MacDougall1, Thomas L. Frölicher2,3, Chris D. Jones4, Joeri Rogelj5,6, H. Damon Matthews7, Kirsten Zickfeld8, Vivek K. Arora9, Noah J. Barrett1, Victor Brovkin10, Friedrich A. Burger2,3, Micheal Eby11, Alexey V. Eliseev12,13, Tomohiro Hajima14, Philip B. Holden15, Aurich Jeltsch-Thömmes2,3, Charles Koven16, Laurie Menviel17, Martine Michou18, Igor I. Mokhov12,13, Akira Oka19, Jörg Schwinger20, Roland Séférian18, Gary Shaffer21,22, Andrei Sokolov23, Kaoru Tachiiri14, Jerry Tjiputra20, Andrew Wiltshire4, and Tilo Ziehn24 Andrew H. MacDougall et al.
  • 1St. Francis Xavier University, Antigonish, B2G 2W5, Canada
  • 2Climate and Environmental Physics, Physics Institute, University of Bern, Switzerland
  • 3Oeschger Centre for Climate Change Research, University of Bern, Switzerland
  • 4Met Office Hadley Centre, Exeter, EX1 3PB, UK
  • 5Grantham Institute for Climate Change and the Environment, Imperial College London, London, UK
  • 6International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria
  • 7Concordia University, Montreal, Canada
  • 8Department of Geography, Simon Fraser University, Burnaby, Canada
  • 9Canadian Centre for Climate Modelling and Analysis, Environment and Climate Change Canada, Victoria, BC, Canada
  • 10Max Planck Institute for Meteorology, Hamburg, Germany
  • 11University of Victoria, Victoria, BC, Canada
  • 12Faculty of Physics, Lomonosov Moscow State University, Moscow, Russia
  • 13A.M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences, Moscow, Russia
  • 14Research Center for Environmental Modeling and Application, Japan Agency for Marine-Earth Science and Technology,Yokohama, Japan
  • 15School of Environment, Earth and Ecosystem Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK
  • 16Climate and Ecosystem Sciences Division, Lawrence Berkeley National Lab, Berkeley, CA, USA
  • 17Climate Change Research Centre, PANGEA, The University of New South Wales, Sydney, Australia
  • 18CNRM, Université de Toulouse, Météo-France, CNRS, Toulouse, France
  • 19Atmosphere and Ocean Research Institute, The University of Tokyo, Japan
  • 20NORCE Norwegian Research Centre, Bjerknes Centre for Climate Research, Bergen, Norway
  • 21Research Center GAIA Antarctica, University of Magallanes, Punta Arenas, Chile
  • 22Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
  • 23Center for Global Change Science, Massachusetts Institute of Technology, Cambridge, USA
  • 24Commonwealth Scientific and Industrial Research Organisation, Oceans and Atmosphere, Aspendale, VIC, Australia

Abstract. The Zero Emissions Commitment (ZEC) is the change in global mean temperature expected to occur following the cessation of net CO2 emissions, and as such is a critical parameter for calculating the remaining carbon budget. The Zero Emissions Commitment Model Intercomparison Project (ZECMIP) was established to gain a better understanding of the potential magnitude and sign of ZEC, in addition to the processes that underlie this metric. Eighteen Earth system models of both full and intermediate complexity participated in ZECMIP. All models conducted an experiment where atmospheric CO2 concentration increases exponentially until 1000 PgC has been emitted. Thereafter emissions are set to zero and models are configured to allow free evolution of atmospheric CO2 concentration. Many models conducted additional second priority simulations with different cumulative emissions totals and an alternative idealized emissions pathway with a gradual transition to zero emissions. The inter-model range of ZEC 50 years after emissions cease for the 1000 PgC experiment is − 0.36 to 0.29 ºC with a model ensemble mean of −0.06 ºC, median of −0.05 ºC and standard deviation of 0.19 ºC. Models exhibit a wide variety of behaviours after emissions cease, with some models continuing to warm for decades to millennia and others cooling substantially. Analysis shows that both ocean carbon uptake and carbon uptake by the terrestrial biosphere are important for counteracting the warming effect from reduction in ocean heat uptake in the decades after emissions cease. Overall, the most likely value of ZEC on multi-decadal timescales is close to zero, consistent with previous model experiments.

Andrew H. MacDougall et al.

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Andrew H. MacDougall et al.

Andrew H. MacDougall et al.

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Short summary
The Zero Emissions Commitment (ZEC) is the change in global temperature expected to occur following the complete cessation of CO2 emissions. Here we use 18 climate models to assess the value of ZEC. For our experiment we find that ZEC 50 years after emissions cease is between −0.36 to 0.29 ºC. The most likely value of ZEC on is assessed to be close to zero. However substantial continued warming for decades or centuries following cessation of CO2 emission cannot be ruled out.
The Zero Emissions Commitment (ZEC) is the change in global temperature expected to occur...
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