The Carbon Dioxide Removal Model Intercomparison Project (CDR-MIP) Initial Results and Future Experiment Designs

Continued anthropogenic greenhouse gas emissions are changing the climate threatening "severe, pervasive and irreversible" impacts. Inadequate emissions reduction is resulting in increased attention on Climate Intervention (CI) - deliberate interventions to counter climate change that seek to either modify the Earth's radiation budget, or remove the primary greenhouse gas from the atmosphere - Carbon Dioxide Removal (CDR). The majority of future scenarios that do not exceed 2°C warming by 2100 include CDR methods. At present, there is little consensus on the efficacy and impacts of CDR and proposed CDR methods. In response, the Carbon Dioxide Removal Model Intercomparison Project (or CDR-MIP) has been initiated. This project brings together a suite of Earth System Models (ESMs) and Earth System Models of Intermediate Complexity (EMICS) in a common framework to explore the potential, risks, and challenges of CDR and different proposed CDR methods. The first set of CDR-MIP experiments investigate climate "reversibility" and the response of the Earth system to idealized engineered permanent CO2 removal. Here we present early results of these experiments and also discuss the design and implementation of the next experiments that explore CDR via land use change and ocean alkalinization. In particular we will highlight which components of the simulated climate system exhibit "reversibility", when CO2 increases and then decreases, and the time scales over which this occurs. Many of the trends are similar in different models; however, there is some disagreement in the response of the simulated carbon cycle.