Accomplished EC-EARTH simulations for CMIP5

The EC-EARTH model has been used during the last months to produce simulations for the on-going Coupled Climate Model Intercomparison Project Phase 5 (CMIP5) in support of the next IPCC Assessment Report. The simulations have been completed and the results meet the expectations. Some post-processing of the output remains before the results can be transferred to the CMIP5 archive for further analysis by the wider scientific community.

The on-going Coupled Model Intercomparison Project Phase 5 (CMIP5) organizes all climate modeling groups in a coordinated effort to simulate the recent past and the future climate. The CMIP5 protocol defines the experiment guidelines that all models are expected follow, for example the change of greenhouse gas concentrations over time. The output from all experiments will be collected in a huge archive that will be stored distributed on a number of data centers.

The CMIP5 data will become accessible for scientific research, and they will be used to gain new insights into the working of climate models and the description of the underlying process. The data will help scientist to separate the climate change signal from natural variability and model uncertainty. The data and the studies made with the data provide support for the upcoming 5th assessment report of the IPCC.

Contribution of both historical and future scenarios from Rossby Centre and MISU

The EC-EARTH consortium contributes to several CMIP5 experiments with the EC-EARTH model (Hazelegger et al. 2010 and 2011). Together, the Rossby Centre and the Meteorological Institution at Stockholm University (MISU) contribute with 3 ensemble members for the historical period 1850-2005, followed by two future RCP scenarios until 2100. In addition to these experiments that contribute to the grand EC-EARTH ensembles with 16 members, the Rossby Centre has also performed a RCP2.6 scenario experiment. The output from these experiments will be made available to the wider scientific community through the CMIP5 archive. In addition, the Rossby Centre will use the results from historical and scenario experiments for later downscaling with the regional climate model RCA.

Climate forcing follows given Representative Concentration Pathways

The ensemble approach takes into account the uncertainty from the unknown initial conditions. All EC-EARTH experiments are done with the same model version, and use the same external forcing, the only difference being the initial state of the ocean in 1850. The initial conditions for the ocean are taken from a long pre-industrial control simulation that has been done previously. The climate forcing follows the CMIP5 protocol. In addition to the changes in GHG and aerosols with time, the variation of the solar radiation, land-use changes and volcanoes are also accounted for. The forcing is constrained by observations until 2005, afterwards it follows a given Representative Concentration Pathway (RCP) scenario (Moss et al. 2010).

Temperature scenarios from EC-EARTH are in line with earlier projections

The time-series for the global annual mean near-surface temperature is shown in Figure 1. The three ensemble members are different when comparing individual years, yet the overall trend is the same, determined by the change in the climate forcing. After 2005, the time-series diverts into three branches, each representing a different RCP scenario. After about 2030, the three scenarios separate and we obtain a different response in the temperature in the second half of the 21st century. The warming since pre-industrial conditions relative to the reference period 1961-1990 is approximately 0.6 degrees, comparable to estimates from observation records. For this century, the temperature increase is expected to be in the range 4.5 deg C (RCP8.5) to 1.2 deg C (RCP2.6) which is in line with earlier projections of climate change (cf. IPCC AR4).

T2m EC-EARTH
Figure 1. Global annual mean 2-m temperature in three EC-EARTH experiments done by MISU and SMHI, relative to the average temperature for the period 1961-1990. The three ensemble members are all done with the same model version, but they start from different initial conditions in 1850. Between 1850 and 2005 (historical period, hist), the model is forced with observed concentrations of greenhouse gases and aerosols. After 2005, the climate forcing follows the RCP85, RCP45 and RCP26 scenario, respectively.
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Data will soon be available at the ESG data portal

The CMIP5 simulations are completed and the results have been transferred to the analysis computer for post-processing. The CMIP5 protocol requests saving monthly and daily means, as well as 6-hourly instantaneous output for selected variables. The results need to be converted from GRIB to netCDF in combination with a controlled vocabulary for filenames and attributes. Once the output is CMOR2 compliant it will be sent to ICHEC that organizes the CMIP5 archive for all contributions from the EC-EARTH community. The data will then become available to the wider climate research community through the ESG data portal.

References

Hazeleger, W., and Coauthors, 2010: EC-Earth: a seamless earth-system prediction approach in action. Bull. Amer. Meteor. Soc., 91, 1357–1363. doi: 10.1175/2010BAMS2877.1

Hazelegger, W. and Coauthors, 2011: EC-Earth V2: description and validation of a new seamless Earth system prediction model. Submitted to Clim.Dyn.

Moss, R.H. and Coauthors, 2010: The next generation of scenarios for climate change research and assessment, Nature, 463, doi:10.1038