The Carbon Dioxide Removal Model Intercomparison Project (CDRMIP): rationale and experimental protocol for CMIP6

Keller, David P.; Lenton, Andrew; Scott, Vivian; Vaughan, Naomi E.; Bauer, Nico; Ji, Duoying; Jones, Chris D.; Kravitz, Ben; Muri, Helene; Zickfeld, Kirsten

doi:10.5194/gmd-11-1133-2018

Cited by 172 publications

(163 citation statements)

References 91 publications

(124 reference statements)

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“…Specifically, the Coupled Climate-Carbon Cycle Model Intercomparison Project includes an "overshoot scenario" and a corresponding BGC variant. There is also a Carbon Dioxide Removal Model Intercomparison Project (Keller et al, 2018), which will provide 1% ramp-down simulations from the end of the 1% ramp-up. It would be extremely interesting if modeling groups participating Carbon Dioxide Removal Model Intercomparison Project could additionally run a BGC (and if possible a RAD) variant of this experiment.…”

Section: Discussionmentioning

confidence: 99%

Ocean Carbon Cycle Feedbacks Under Negative Emissions

Schwinger

Tjiputra

2018

Geophysical Research Letters

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Negative emissions will most likely be needed to achieve ambitious climate targets, such as limiting global warming to 1.5°. Here we analyze the ocean carbon‐concentration and carbon‐climate feedback in an Earth system model under an idealized strong CO2 peak and decline scenario. We find that the ocean carbon‐climate feedback is not reversible by means of negative emissions on decadal to centennial timescales. When preindustrial surface climate is restored, the oceans, due to the carbon‐climate feedback, still contain about 110 Pg less carbon compared to a simulation without climate change. This result is unsurprising but highlights an issue with a widely used carbon cycle feedback metric. We show that this metric can be greatly improved by using ocean potential temperature as a proxy for climate change. The nonlinearity (nonadditivity) of climate and CO2‐driven feedbacks continues to grow after the atmospheric CO2 peak.

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Section: Discussionmentioning

confidence: 99%

Ocean Carbon Cycle Feedbacks Under Negative Emissions

Schwinger

Tjiputra

2018

Geophysical Research Letters

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“…The Carbon Dioxide Removal Model Intercomparison Project (CDRMIP) was created to coordinate and advance the understanding of CDR in the Earth system (Lenton et al, 2017). CDRMIP brings together Earth system models of varying complexity in a series of coordinated multimodel experiments, one of which is a global AOA experiment (CDR_4) (Keller et al, 2018). This will allow the response of the Earth system to AOA to be further explored and quantified in a robust multi-model framework, and will examine important further questions such as including cessation effects of alkalinity addition, and the long-term fate of additional alkalinity in the ocean.…”

Section: Summary and Concluding Remarksmentioning

confidence: 99%

Assessing carbon dioxide removal through global and regional ocean alkalinization under high and low emission pathways

et al. 2018

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Abstract. Atmospheric carbon dioxide (CO 2 ) levels continue to rise, increasing the risk of severe impacts on the Earth system, and on the ecosystem services that it provides. Artificial ocean alkalinization (AOA) is capable of reducing atmospheric CO 2 concentrations and surface warming and addressing ocean acidification. Here, we simulate global and regional responses to alkalinity (ALK) addition (0.25 PmolALK yr −1 ) over the period 2020-2100 using the CSIRO-Mk3L-COAL Earth System Model, under high (Representative Concentration Pathway 8.5; RCP8.5) and low (RCP2.6) emissions. While regionally there are large changes in alkalinity associated with locations of AOA, globally we see only a very weak dependence on where and when AOA is applied. On a global scale, while we see that under RCP2.6 the carbon uptake associated with AOA is only ∼ 60 % of the total, under RCP8.5 the relative changes in temperature are larger, as are the changes in pH (140 %) and aragonite saturation state (170 %). The simulations reveal AOA is more effective under lower emissions, therefore the higher the emissions the more AOA is required to achieve the same reduction in global warming and ocean acidification. Finally, our simulated AOA for 2020-2100 in the RCP2.6 scenario is capable of offsetting warming and ameliorating ocean acidification increases at the global scale, but with highly variable regional responses.

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“…The addition of alkalinity in our AOA2070 experiment is large compared with AOA simulations in previous studies: fivefold larger than in Hauck et al (), over half of the integration time, that is, 300 Pg during 100 years versus 1,580 Pg over 50 years assuming olivine as source of alkalinity. In comparison with the addition of alkalinity defined in the Carbon Dioxide Removal Model Intercomparison Project (Keller et al, ), we assume a total addition 6 times larger. However, actual availability of raw alkaline materials does not pose the major feasibility issue that AOA faces but rather the associated high logistic costs and environmental problems caused by the mining, production, and release of alkalinity compounds in seawater (e.g., Hartmann et al, ; Renforth & Henderson, ).…”

Section: Methodsmentioning

confidence: 99%

Enhanced Rates of Regional Warming and Ocean Acidification After Termination of Large‐Scale Ocean Alkalinization

González

Ilyina

Sonntag

et al. 2018

Geophysical Research Letters

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Termination effects of large‐scale artificial ocean alkalinization (AOA) have received little attention because AOA was assumed to pose low environmental risk. With the Max Planck Institute Earth system model, we use emission‐driven AOA simulations following the Representative Concentration Pathway 8.5 (RCP8.5). We find that after termination of AOA warming trends in regions of the Northern Hemisphere become ∼50% higher than those in RCP8.5 with rates similar to those caused by termination of solar geoengineering over the following three decades after cessation (up to 0.15 K/year). Rates of ocean acidification after termination of AOA outpace those in RCP8.5. In warm shallow regions where vulnerable coral reefs are located, decreasing trends in surface pH double (0.01 units/year) and the drop in the carbonate saturation state (Ω) becomes up to 1 order of magnitude larger (0.2 units/year). Thus, termination of AOA poses higher risks to biological systems sensitive to fast‐paced environmental changes than previously thought.

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The Carbon Dioxide Removal Model Intercomparison Project (CDRMIP): rationale and experimental protocol for CMIP6

Abstract: Abstract. The recent IPCC reports state that continued anthropogenic greenhouse gas emissions are changing the climate, threatening "severe, pervasive and irreversible" im-

Cited by 172 publications

References 91 publications

Ocean Carbon Cycle Feedbacks Under Negative Emissions

Ocean Carbon Cycle Feedbacks Under Negative Emissions

Assessing carbon dioxide removal through global and regional ocean alkalinization under high and low emission pathways

Enhanced Rates of Regional Warming and Ocean Acidification After Termination of Large‐Scale Ocean Alkalinization

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