Global Climate Modelling

The Danish Climate Centre (DKC) uses Global climate models (GCMs) to investigate interactions between atmosphere, ocean, land surface and ice. We study interannual to multi-decadal climate fluctuations and predictability and project future climate as consequences of external influences such as the anthropogenic greenhouse effect.

To better model feedback effects, the GCM is often coupled to models of other processes, such as the surface hydrological cycle, ice sheets and/or the carbon cycle.

The accuracy of future GCM projections relies highly on our understanding of how internal variability and external forcings in the Earth's climate system function, and how they will evolve in the future. Therefore, we constantly seek to expand and improve the global climate models in step with our understanding of the processes influencing the climate system.

Focus areas

Regional Climate Modelling

Global Climate Modelling

Ozone, UVR and Climate

Radio Occultations

Ice Sheet Modelling

Processes in the Arctic

Developing Countries

Climate Data Host

The EC-Earth initiative

We are participating in several international research projects involving GCM development and applications. One of these projects is the EC-Earth initiative, which involves 22 different research institutions from more than 10 European countries.

The EC-Earth initiative aims at establishing a European Earth System Model based on the Numerical Weather Prediction System of the European Centre for Medium-Range Weather Forecasts(ECMWF). In concerted effort, researchers in the EC-Earth consortium are developing, evaluating and improving the model system.

The core of the EC-Earth model is a fully coupled atmosphere-ocean-sea ice model system. The EC-Earth core system consists of ECMWF’s Integrated Forecast System (IFS). The standard configuration runs at T159 horizontal spectral resolution with 62 vertical levels for the atmosphere, and 1 degree and 42 vertical levels for the ocean and sea ice. Details on the complete system can be found through the EC-Earth link.

This core system is used to produce new climate change simulations as specified by the Coupled Model Intercomparison Project Phase 5 (CMIP5) for the next IPCC assessment report.

In the EC-Earth consortium, the DKC is represented in the Steering Group, the Technical Issues working group and in the CMIP5 working group.

CMIP5 control simulation

We have performed a 750-year long pre-industrial CMIP5 control simulation using the EC-Earth model. A number of CMIP5-type climate change experiments forced with CMIP5 specified boundary conditions for greenhouse gasses, sulphate aerosols, land use and solar irradiance (i.e., only volcanic aerosol concentrations are missing in the CMIP5 specified forcings) have also been carried out.

The Figure illustrates the global averaged annual surface air temperature anomalies with respect to period 1961 to 1990.The figure shows global averaged annual surface air temperature anomalies as simulated in three CMIP5-tupe historical experiments (in red, blue and cyan) for the period 1850-2005 and experiments forced with Representative Concentration Pathway (RCP) 4.5 (in purple) and RCP 8.5 scenarios (in magenta) for the period 2006-2100, respectively. Also plotted in the figure are observations from the Climate Research Unit dataset (in black). Two of the three historical experiments (red and blue) only differ in the initial state selected from a 500 year preindustrial control run. The third historical experiment (cyan) uses the EC-Earth model with a configuration that includes a better resolved stratosphere. The RCP 4.5 and RCP 8.5 experiments started from the end of one of the historical run (red), respectively.

The COMBINE project

Another project that we are involved in is the European FP7 supported COMBINE project.

This project brings together research groups to advance Earth system models for more accurate climate projections and to reduce uncertainty in the prediction of climate and climate change in the coming decades.

In the project, we work on coupling an ice sheet model for Greenland and Antarctica ice sheets to EC-Earth, and expanding the atmosphere module vertically to include a better resolved stratosphere.

A comparison of simulation results and observations shows that the new version of the atmosphere model better simulates the mean temperature and winds in the stratosphere and the upper troposphere. The feedbacks and influence of these components in the EC-Earth will be investigated during the course of the project.

Contacts

For further information contact Shuting Yang, shuting@dmi.dk
Phone: (+45) 39157 463

Edited by Tue Tobias Kosack, ttk@dmi.dk © DMI, 12 May 2011