Preprints
https://doi.org/10.5194/bg-2021-136
https://doi.org/10.5194/bg-2021-136

  26 May 2021

26 May 2021

Review status: this preprint is currently under review for the journal BG.

Estimated effect of the permafrost carbon feedback on the zero emissions commitment to climate change

Andrew Hugh MacDougall Andrew Hugh MacDougall
  • St. Francis Xavier University, Antigonish, B2G 2W5, Canada

Abstract. Zero Emissions Commitment (ZEC), the expected change in global temperature following the cessation of CO2 emissions has recently been assessed by the Zero Emissions Commitment Model Intercomparison Project (ZECMIP). ZECMIP concluded that the component of ZEC from CO2 emissions will likely be close to zero in the decades following the cessation of emissions. However, of the 18 Earth system models that participated in ZECMIP only two included a representation of the permafrost carbon feedback to climate change. To better assess the potential impact of permafrost carbon decay on ZEC a series of perturbed parameter experiments are here conducted with an Earth system model of intermediate complexity. The experiment suggest that the permafrost carbon cycle feedback will directly add 0.06 [0.02 to 0.14] °C to the benchmark ZEC value assesses 50 years after 1000 PgC of CO2 has been emitted to the atmosphere. An additional 0.04 [0 to 0.06] °C is likely to been added relative to the benchmark ZEC value from the thaw-lag effect unaccounted for in the ZECMIP experiment design. Overall we assess that the permafrost carbon feedback is unlikely to change the assessment that ZEC is close to zero on decadal timescales, however the feedback is expected to become more important over the coming centuries.

Andrew Hugh MacDougall

Status: open (until 17 Jul 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Andrew Hugh MacDougall

Andrew Hugh MacDougall

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Short summary
The permafrost soils hold about twice as much carbon as the atmosphere, as the Earth warms the organic matter in these soil will decay releasing CO2 and CH4. It is expected that these soil will continue to release carbon into the atmosphere long after emissions cease. Here we use a method where hundreds of slightly varying model versions to estimate how much warming permafrost carbon will cause after human emissions of CO2 end.
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