EC-Earth
Earth System Models such as EC-Earth are currently the only way of providing society with information on the future climate. EC-Earth generates projections of global climate change, which are a prerequisite to support the development of national adaptation and mitigation strategies.
EC-Earth is a global climate model system based on the idea to use the world-leading weather forecast model of the ECMWF, European Centre of Medium Range Weather Forecast, in its seasonal prediction configuration as the base of climate model. The model system can be used in several configurations including the classical climate model, icluding atmosphere, soil, ocean and sea ice, and Earth System configurations, adding atmospheric chemistry and aerosols, ocean bio-geo-chemistry, dynamic vegetation and a Greenland ice sheet. The model is developed by the European EC-Earth consortium with SMHI as core partner leading the development and other Swedish partners from the universities of Lund, Stockholm, Gothenburg and Uppsala. The model in its different configurations and resolutions is used for climate change projections, predictions and process studies. EC-Earth 3, the current version, is prepared for the 6th phase of the Climate Model Intercomparison Project CMPI6.
Read more about CMIP6 (wcrp-cmip.org)
External link.
Model description
The EC-Earth Earth System Model (ESM) describes the global climate system and its evolution in time by a combination of coupled physical and biogeochemical processes. The current version EC-Earth 3 is based on:
- ECMWF's atmospheric circulation model IFS, cycle 36r4, including the land surface model H-Tessel.
- The current version of the ocean model NEMO3.6, including the Louvain-la-Neuve Sea Ice Model (LIM3).
- The PISCES v2 ocean bio-geo-chemistry component.
- The dynamical vegetation model LPJ-GUESS v4.
- The atmosphere composition and aerosol model TM5.
- The PISM 0.7 ice sheet model.
The model components are coupled via the Oasis-3 MCT coupler.
Model development
The development of the EC-Earth model is a shared task of the EC-Earth community, currently lead by SMHI. The community is organized in work groups (WGs) lead by the Steering Group (SG). Both WGs and SG maintain a communication with corresponding entities at ECMWF and the NEMO team to ensure benefits for both sides.
Since EC-Earth v2.3, the CMIP5 version, all model components have been upgraded and the way of collaboration within the growing consortium has been greatly facilitated. In an effort to make the complex model more suitable for new users and a growing community, a number of technical aspects have been reconsidered. EC-Earth 3 comes with a greatly simplified configuration procedure and build system, including a graphical user interface, which allows an easy to use and interactive way of configuration. Moreover, portability of EC-Earth 3 has been addressed and is substantially improved.
Acknowledging the fact that scientific software development is a complex matter, the development process itself has been adapted to follow established best practices for software projects as far as possible. As a result, all development activities are now directed to the EC-Earth 3 Development Portal, a web based service that covers version control, issue tracking, documentation, and other means of communication between users and developers.
Focus areas of model development are a number of flexible model configurations such as different combinations of ESM model components and resolutions, good climate performance of standalone and coupled configurations and the full implementation of CMIP6 standard forcing and output standards.
Model tuning as part of the model development applies a number of constraints such as energy and mass budgets close to observations, at the top of the atmosphere and at the surface, in particular between atmosphere and ocean. Model biases such as for temperature, precipitation and circulation are minimized.
Model evaluation
Different model configurations are tuned towards observed climate conditions. The resulting model is then subject to a spin-up under pre-industrial conditions, followed by a historical simulation between 1850 and today. Those simulations are to be carried out during autumn 2017. The resulting climate performance will then be analysed by standard diagnostics focusing on global and regional biases, seasonal cycles, climate sensitivity, climate modes of variability, and predictive capability.
Application of EC-Earth
After the model evaluation, model experiments in line with CMIP6 tasks will be carried out. SMHI is most interested in new climate scenarios following the emission scenario framework of Shared Socio-economic Pathways. Previous climate scenario simulations have been carried out with an older version of EC-Earth and different forcing datasets.
Recently:
- Links between Arctic surface variability and its interaction with lower latitudes have been examined.
- The sensitivity to Arctic sea ice changes on European climate variability at different global surface warming levels have been explored.
- The sensitivity of the west African and South Asian monsoon to model resolution has been explored.
- Changes in climate variability and extremes at the 3 warming levels have been examined.
- Effects of increased resolution in Earth system models in general and more specifically on Southern Ocean variability has been tested.
Different configurations of the EC-Earth models are used in Swedish, Nordic, European and other international projects such as CRESCENDO, PRIMAVERA and IMPREX for climate scenarios, climate prediction experiments and climate process studies. Results are key input to climate change information for national and international stakeholders and for climate services. Furthermore, the global model simulations with EC-Earth deliver boundary conditions for further downscaling by regional climate models.