Outcome Advisory Board meeting:�Key research questions/themes

Type #1 - Asymmetry in Earth system responses to emissions vs removal pulses

Type #2 - Activity-driven CDR implementations of IAM-developed scenarios

Type #3 - CO₂ removal effectiveness of individual CDR measures for different climates

Type #4 - CDR in overshoots with and without SRM (not pursuing in CDRMIP)

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Asymmetry in Earth system reactions

to emissions vs removal pulses

Tier 1:

• Compare asymmetry of temperature and Earth system responses to a large pulse with additions or removals of CO₂
• Disentangle the contribution from the transient disequilibrium
• Understand the effects of state dependency
• Provide ESM simulations for the calibration of simple climate models (emulators)

Tier 2:

• Direct ocean vs air removal experiment
• Understand the effects of state dependency

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Asymmetry in Earth system reactions

to emissions vs removal pulses

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Tier 1:

• building on C4MIP fast-track esm-flat10-zec

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• Same experiment with a budget of 2000 PgC emitted (esm-flat10-brch2000-pulse-500(-neg))

• CDRMIP experiment:
• 100 years of esm-flat10 (at 1000 PgC emitted) followed by a removal pulse of 500 PgC (esm-flat10-brch1000-pulse-500-neg)

• 100 years of esm-flat10 (at 1000 PgC emitted) followed by a emissions pulse of 500 PgC (esm-flat10-brch1000-pulse-500)

Tier 2:

• building on C4MIP esm-flat10-zec

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Asymmetry in Earth system reactions

to emissions vs removal pulses

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• CDRMIP experiment:
• 100 years of flat10 (1000PgC emitted) followed by a removal of 500PgC from the surface of the ocean (esm-flat10-brch1000-pulse-500-neg-actDOR)

• repeat the emissions and removal pulses for other cumulative carbon emissions budgets (at 750PgC and 1500 PgC) (esm-flat10-brch750/1500-pulse-500-(neg))

Activity-driven CDR implementations of IAM-developed scenarios

Tier 1:

• Evaluate impacts and uncertainties of resolving activity-driven BECCS in policy-relevant ambitious mitigation scenarios (i.e. ScenarioMIP)
• Quantify CDR mismatch between IAMs & ESMs in a multi-model context
• Investigate the impact of climate change on yields and BECCS effectiveness

Tier 2:

• Consider a portfolio implementations of terrestrial CDR and marine CDR

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Activity-driven BECCS in Scenario-MIP experiment

Tier 1 (esm-scen7-ln-actBECCS):

• building on ScenarioMIP low to negative (LN) scenario
• CDRMIP experiment:
• emissions-driven & activity-driven BECCS in ScenarioMIP-LN scenario
• activity-driven BECCS implementations in ESM based on energy crops
• yields from BE crops to be stored in a permanent carbon pool (incl. loss terms)
• omit net-negative BECCS emissions from esm-scen7-ln in the ESM emission forcing

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Activity-driven OAE in IAM scenario

Tier 2:

• expanding the IAM scenario with Ocean Alkalinity Enhancement (OAE)

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• CDRMIP experiments:
1. emissions-driven IAM scenario with activity-driven OAE �(including gross emissions from calcification and spatially �resolved OAE implementation) (esm-scen7-ln-REMINDMAgPIE-actOAE)
2. emissions-driven IAM scenario no-OAE baseline (omit OAE implementation including positive emissions related to the process) (esm-scen7-ln-REMINDMAgPIE)
3. concentration-driven no-OAE baseline (CO₂ concentrations �from 1, no OAE implementation) (scen7-ln-REMINDMAgPIE)

CDR effectiveness of individual measures for different climates

Tier 1:

• Quantify CDR effectiveness of a given activity-driven CDR implementation under net-zero
• Assess the Earth system responses (incl. biogeophysical) to the CDR implementation
• Bonus: investigate the partitioning of ocean and land carbon sinks under land-use vs no-land-use flat10 experiments
• Test CDR effectiveness under increasing and decreasing atmospheric CO₂

Tier 3:

• Investigate further selected CDR options

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CDR removal effectiveness under net-zero

Tier 1 (flat10-LUC-zec-act**CDR**, e.g.ARF):

• all experiments will be concentration-driven prescribed from esm-flat10-zec
• CDRMIP experiment:
1. apply LUH3 from last 100 years of historical land-use

to flat10 and constant thereafter (flat10-LUC & flat10-LUC-zec)

• during zero emissions phase convert to dominant forest type x% of all agricultural area and grassland

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CDR removal effectiveness experiments

Tier 1:

• concentration-driven prescribed from esm-flat10-zec
• CDRMIP experiments:
• agricultural land and grassland afforestation/reforestation experiment (details see slide #10) (flat10-LUC-zec-actARF)
• conversion of agricultural land and grassland to BECCS experiment (flat10-LUC-zec-actBECCS)
• annually repeating coastal, uniform ocean alkalinity addition based onthe OAE-MIP mask (flat10-LUC-zec-actOAE)

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CDR removal effectiveness experiments

Tier 1:

• concentration-driven prescribed from from extended esm-flat10
• CDRMIP experiments:
• agricultural land and grassland afforestation/reforestation experiment (details see slide #10) (flat10-LUC-actARF)
• conversion of agricultural land and grassland to BECCS experiment (flat10-LUC-actBECCS)
• annually repeating coastal, uniform ocean alkalinity addition based onthe OAE-MIP mask (flat10-LUC-actOAE)

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CDR removal effectiveness experiments

Tier 3:

• concentration-driven prescribed from esm-flat10(-zec)
• proposed CDRMIP experiments:
• annually repeating macroalgae open-ocean mariculture and sinking in defined areas at the max scale (flat10-LUC(-zec)-actMOS)
• annually repeating enhanced rock weathering at max theoretical rates (flat10-LUC(-zec)-actERW)
• annually repeating coastal uniform direct ocean removal at max theoretical rates (flat10-LUC(-zec)-actDOR)

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