RT Leaders: Guy Brasseur (MPIMET, Hamburg) Jean-Francois Royer (CNRM, Toulouse)

1. Research Theme RT2A:Production of seasonal to decadal hindcasts and climate change scenarios (Model Engine Part 1) RT Leaders: Guy Brasseur (MPIMET, Hamburg) Jean-Francois Royer (CNRM, Toulouse)

2. Aims of RT2A • Produce sets of global climate simulations with all major European coupled GCMs • Provide multi-model results needed in other RTs

3. Organization of the work Stream 1 Year 1-2 Use existing coupled models Standard methods for simulations Use scenarios from IPCC Stream 2 Year 3-4 Improved earth system models (RT1) Methods of ensemble generation (RT1) Updated scenarios (RT7)

4. IPCC scenarios (TAR) 4xCO2 A2 A1B B1 2xCO2 20C3M Control

5. Primary objectives (1) • Production of a set of multi-model simulations at seasonal-decadal time scales • Production of a first set of multimodel simulations of future long-term climate change scenarios for the 21st century • Use of the ensemble prediction system and methodologies provided by RT1, and new scenarios of greenhouse gas emission and land use change produced by RT7 to perform new simulations on both seasonal-decadal and centennial time scales

6. Primary objectives (2) • Provision of model simulations for use as boundary conditions for regional models (RT2B, RT3), for the study of feedbacks processes (RT4) and validation (RT5), to drive impact models (RT6) and for scenario and policy implications (RT7) • Development of a comprehensive database with public access for multi-model climate simulations at seasonal, decadal and longer time scales

7. Combination of atmosphere-ocean models used to produce the coupled simulations in RT2A

8. RT2A Workpackages • WP2A.0: RT2A Coordination activities (leaders: Guy Brasseur, JF Royer) • WP2A.1: Creation of multi-model seasonal to decadal hindcasts - Leader: Philippe Rogel (CERFACS) • WP2A.2: Creation of multi-model hindcasts for the 20th Century, including variations in external forcing -Leader: Eigil Kaas (DMI) • WP2A.3: Creation of multi-model climate change scenarios for the 21st Century that exploit the probabilistic nature of the multi-model ensemble system - Leader: Ulrich Cubasch (FUB) • WP2A.4: Storage, extraction and creation of distributed databases for provision of the results -Leader: Francisco Doblas-Reyes (ECMWF)

9. Participants to RT2A WPs

10. Links with other RTs New models and methods RT1 Simulated datasets RT4 RT5 RT6 RT2A RT7 Updated scenarios Boundary conditions RT2B RT3

11. Inputs required from other RTs ·  A list of output fields needed in the other RTs. Required by start of year 1 in order to secure the storage of the appropriate field in stream 1 simulations ·  ESM ensemble system developed by RT1: required by WP2A.1, WP2A.2 and WP2A.3 by start of year 3. ·  New global scenarios for 2000-2100 from RT7: required by WP2A.3 by start of year 4. ·  An update of the output fields list for the other RTs. Required by start of year 3 for stream 2 simulations

12. Output required by other RTs ·  Forcing fields needed as boundary conditions for regional models in RT2B and RT3 over the period 1950-2100 by start of year 3 ·  GCM results from the first stream of simulations will be provided to RT4, RT5, RT6, RT7 from the start of year 2 for climate hindcasts, and start of year 3 for climate scenarios · GCM output from the second stream of simulations will be provided to RT4,RT5, RT6, RT7 from the start of year 4 onwards

13. Major milestones over full project duration • Provision of a first stream of updated climate simulations • Expected deliverable:Results of the climate predictions, simulations and scenarios from the different modelling centers (month 24). • Provision of a second stream of updated climate simulations • Expected deliverables:Results of the new multi-model multi-ensemble climate simulations archived in database at ECMWF and MPI-MD (month 48). • Dissemination of model results • Expected deliverables:Selected results of the multi-model multi-ensemble climate simulations archived in a database at ECMWF and MPI-MD (month 60)

14. First 18 Months: Deliverables • D2A.0: Development of the RT2A Website • D2A.1: Several years of ocean analyses to be used as initial conditions for the seasonal-to-decadal hindcast production • D2A.2: Simulations based on existing atmospheric and coupled ocean-atmosphere-sea ice models over the past 100 years (mean climate, interannual variability, and trends) • D2A.3: First set of scenarios experiments for the prediction of future climate, using existing coupled ocean-atmosphere climate models • D2A4.1: Definition of a list of variables and one or two formats for storage of model results. • D2A4.2: Description of the formats (data and metadata) to be used within ENSEMBLES

15. First 18 Months: Milestones and expected results • M2A.1: Specification of a common list of field to be stored to fulfill the needs of other RTs (month 1) • M2A.2: Choice of a common set of forcings to be used for the simulations of 20th century climate (month 2) • M2A.3: Choice of the scenarios for ensemble simulations of 21st century climate (month 12)

16. Preliminary work Pre-project meeting 19-20 January 2004 at DMI • Discussions through the ensembles_rt2a mainling list • RT2A Website with internal member pages for sharing of information and datasets • Choice of a common set of forcings • List of model variables to store • Provisional time-table of simulations