The first stage of CDRMIP will undertake four sets of experiments:
Carbon cycle and climate reversibility experiment (CDR-reversibility): This experiment is based on the CMIP Diagnostic, Evaluation, and Characterization of Klima (DECK) experiment and involves a 1% increase in atmospheric CO2, from the pre-industrial until 4xCO2, and then a 1% removal rate until pre-industrial levels are reached again.
Direct–air capture experiments (CDR-pi-pulse, CDR-yr2010-pulse, and CDR-overhoot): These experiments allow atmospheric CO2 to freely evolve in the models to investigate C cycle and climate feedbacks in response to CDR. The first experiments are designed to investigate the response of the atmosphere to instantaneous CO2 removal, i.e., negative pulses. The next experiment will investigate CDR in the SSP5-3.4-OS “overshoot” scenario.
Afforestation experiment (CDR-afforestation): This experiment combines the high CO2 emission scenario, SSP5-8.5, with a future land use change scenario from an alternative SSP scenario, SSP1-2.6, which has greater afforestation than in the original SSP5 land use projection. The proposed afforestation experiment is similar to the LUMIP Phase Two (Tier 1) experiment esm-ssp585-ssp126Lu. However, a notable difference between our protocol and that of LUMIP is that we will recommend that groups include the SSP5-8.5 and SSP1-2.6 extensions to the year 2300 instead of stopping in the year 2100 as per the LUMIP protocol.
Ocean alkalinization experiment (CDR-ocean-alk): During the SSP5-8.5 emissions scenario (driven from the pre-industrial with emissions) starting in 2020, add 0.25 Pmol yr-1 of alkalinity to the ocean for an 80+ year period. The control simulation would follow the SSP5-8.5 emissions scenario until 2100. Optional: In 2070 the alkalinity addition would cease, and the simulations would continue until or beyond year 2100.
A more detailed general description of the scientific focus and research questions and how these questions apply to individual experiments can be downloaded here.
All groups will be encouraged to undertake all simulations, although individual groups may not be able to complete some experiments and this would not preclude participation. We also encourage those running Earth system models of intermediate complexity (EMICS), as well as box models, to participate and contribute when applicable. The potential to modify or extend the simulations to harness the capability of EMICs and box models to conduct multiple simulations is open for discussion.
The model simulations will be publicly available and hosted on the Earth System Grid Federation (ESGF).