The Geoengineering Model Intercomparison Project Phase 6 ( GeoMIP 6 ) : simulation design and preliminary results

We present a suite of new climate model experiment designs for the Geoengineering Model Intercomparison Project (GeoMIP). This set of experiments, named GeoMIP6 (to be consistent with the Coupled Model Intercomparison Project Phase 6), builds on the previous GeoMIP project simulations, and has been expanded to address several further important topics, including key uncertainties in extreme events, the use of geoengineering as part of a portfolio of responses to climate change, and the relatively new idea of cirrus cloud thinning to allow more longwave radiation to escape to space. We discuss experiment designs, as well as the rationale for those designs, showing preliminary results from individual models when available. We also introduce a new feature, called the GeoMIP Testbed, which provides a platform for simulations that will be performed with a few models and subsequently assessed to determine whether the proposed experiment designs will be adopted as core (Tier 1) GeoMIP experiments. This is meant to encourage various stakeholders to propose new targeted experiments that address their key open science questions, with the goal of making GeoMIP more relevant to a broader set of communities. Published by Copernicus Publications on behalf of the European Geosciences Union. 3380 B. Kravitz et al.: GeoMIP6: simulation design and preliminary results

The Geoengineering Model Intercomparison Project Phase 6 (GeoMIP6) G1ext: How would geoengineering affect changes in less easily detectable climate features, such as extreme events, modes of natural variability, and regional impacts? Quantifying chemistry and aerosols in the CMIP6 models Ocean Model Inter--comparison Project (OMIP) Co--chairs Gokhan Danabasoglu (NCAR, USA), Stephen M. Griffies (NOAA/GFDL, USA), and James Orr (IPSL, France) • OMIP addresses the CMIP6 science quesMon on invesMgaMng the origins and consequences of systemaMc model biases.
• Among the WCRP Grand Challenges (GCs), OMIP directly contributes to the decadal climate variability and predicMon topic which is being considered as a new GC.
• OMIP is independent of any CMIPX.
OMIP includes the previously separate Ocean Carbon Model Inter--comparison Project (OCMIP). This merging of ocean physical, chemical, and biogeochemical efforts into a single project allows for efficient communicaMon across these communiMes parMcipaMng in CMIP6.

Goals
Develop updated historic and future harmonized land use dataset and execute series of idealized and realis@c simula@ons designed to address the following ques@ons and topics:

Main Ques/ons
• What are the effects of land use and land--use change on climate and biogeochemical cycling (past--future)? • Are there regional land management strategies with promise to help mi@gate and/or adapt to climate change? • (What are the effects of climate on land--use and land--use change?) Addi/onal focal topics • Assess rela@ve contribu@on of fossil fuel vs. land use change to climate and BGC • Isolate biogeochemical vs. biogeophysical impacts of land use • Explore land cover change vs. land management change impacts • Assess how land use impact is modulated by land--atmosphere coupling strength • Determine extent that global CO 2 fer@liza@on is modulated by land use change Subgrid data request LUMIP is reques@ng sub--grid informa@on for four sub--grid categories (i.e., @les)for selected variables to permit more detailed analysis of land--use induced surface heterogeneity. The four categories are: (1) Primary and secondary land    Our goal is to disentangle variability in radiative forcing from variability in response in CMIP models Activity 1: Characterize effective radiative forcing using fixed SST atmos. model integrations Tier 1:180 y to diagnose present-day forcing in detail Tier 2: ~750 y to diagnose time-varying forcing, 60 y to diagnose aerosol linearity Lightweight specialized diagnostics to help diagnose adjustments (especially clouds) Activity 2: Assess the accuracy of clear-sky forcing against reference calculations Offline radiative transfer calculations to assess parameterization accuracy in clear, clean skies Provide highly-detailed snapshots for assessment of aerosol radiative transfer RFMIP will provide reference line-by-line calculations These DAMIP experiments and synergies with other MIPs are important to understand "the Earth system respond to forcing (CMIP6-1)", "the origins and consequences of systematic model biases (CMIP6-2)" and assess "future climate changes (CMIP6-3)".  • AOGCM intercomparison project aiming to account for spread in simulated ocean response to changes in surface fluxes resulting from CO 2 forcing.

Decadal Climate Prediction Project (DCPP)
• Targets the CMIP6 science question on the Earth system response to forcing, and of particular relevance to the WCRP Grand Challenge on sea level rise and regional impacts.
• Prescribed set of surface flux perturbations (of momentum, heat and freshwater), applied separately to the ocean water surface, obtained from the ensemble-mean changes simulated at time time of doubled CO 2 by CMIP5 AOGCMs under the 1pctCO2 scenario.
Change in ocean dynamic topography after 100 years under 1pctCO2 in CMIP5 Ensemble mean 2 x ensemble standard deviation obs4MIPs Governance Overview WCRP has taken interest in broadening par2cipa2on in obs4MIPs. To help guide this opportunity, the WCRP's Data Advisory Council (WDAC) has cons2tuted an interna2onal task team to provide stewardship for the advancement of obs4MIPs.
*Contributions from CFMIP-OBS http://climserv.ipsl.polytechnique.fr/cfmip-obs/ Related efforts for reanlayses Ana4MIPS: A CoG "peer project" with obs4MIPs, providing a collec2on of fields from selected major reanalysis well suited for comparison with CMIP simula2ons (mostly dynamical fields). CREATE--IP: A resource for reanalysis data in a centralized loca2on on NASA's NCCS Advanced Data Analy2cs Plamorm (ADAPT), standardizing data formats, providing analy2c and visualiza2on capabili2es, and overall improved access to many fields from reanalysis datasets.

FacilitaAng the CF/CMOR/ESGF preparaAon of obs data
• CMOR3 is currently developing at PCMDI for use in CMIP6. It is being generalized to be useful for preparing observa2onal data. It will include: • A version of CMOR that is accessible via python • Templates for defining global aIributes • Numerous examples (including data) to facilitate ease of use • Task team with the help of others is developing a proposal for describing observa2onal data (via the CF conven2on) in coordina2on with CMIP