Experimental Design for CMIP6: Aerosol, Land Use and Future Scenarios

The CMIP6 meeting continued and deepened discussion on the subject of model intercomparison projections (MIPS) for climate models. Intended to inform understanding of climate change mitigation, adaptation, and impacts, the workshop explored questions about the significance of regional forcings from land use change and air pollutants such as aerosols.

Keywords: atmospheric composition; climate variability and change; models and modeling

Motivation
At the 2013 AGCI meeting on CMIP6, a basic structure for the exercise was developed that involved a central set of model experiments and a number of specialized model intercomparison projections (MIPs). Three of those MIPs are essential to the process of producing integrated scenario analyses of climate change mitigation, adaptation, and impacts: MIPs on land use (LUMIP), tropospheric aerosols chemistry (AerChem MIP), and scenarios (Scenario MIP). These scenarios will be used by hundreds of researchers and practitioners for impact and integrated assessment analyses.

This follow up session at AGCI in 2014 is designed to produce proposals from each of these MIPs for coordinated sets of model experiments to perform as part of CMIP6, and to inform a possible IPCC AR6. Planning within each of these MIPs has already begun, and it is clear that to maximize success, these plans need to be coordinated across the three groups.

The questions to explore regard the significance of changes brought about by regional forcings from both land use and air pollutants, the type of experiment that the two specific MIPs could run in order to aid Scenario MIP to identify a set of future scenarios to propose as part of CMIP6 experimental design. Another key aspect will be a consensus on the approach(es) for the documentation of radiative forcing for all aspects (land use, short-lived climate forces, and well-mixed greenhouse gases).

Involvement
This workshop will involve representatives of the three MIPs (a total of about 20
participants, and additional invited participants that will address specific scientific questions (e.g., statisticians familiar with signal-to-noise methodology and experimental design, integrated assessment modelers, atmospheric chemists) or represent specific groups (e.g., WGCM).

Relevance
The relevance of this activity consists of identifying a small, effective and efficient subset of experiments that are worth running on the part of modeling centers, both in preparation for and as part of the future scenarios choice.

Results of this meeting would consist of proposals for model experiments to be carried out by LUMIP, Chemistry MIP, and Scenario MIP that would be synergistic and successfully inform the wider scenario process. These proposals would feed directly into the WGCM meeting to be held in October 2014, where proposals from these three MIPs will be considered for approval by the CMIP panel.

Structure
Our tentative agenda will consist of 2 days with parallel sessions for each MIP, 1 day reporting on each to the combined group, and 2 days as a combined group working on shared plans.

Workshop organizing committee
Claudia Tebaldi (co-chair, ScenarioMIP), Brian O’Neill (co-chair, ScenarioMIP), Jean-François Lamarque (co-chair, AirChemMIP and member, ScenarioMIP), George Hurtt (co-chair, LUMIP and member, ScenarioMIP), Dave Lawrence (co-chair, LUMIP), Veronika Eyring (CMIP chair and co-chair, ScenarioMIP).