This project will advance the understanding of the greenhouse gas (GHG) effect on climate variability from preindustrial (1850) until the near future (2100). By linking GHG in terrestrial, freshwater and marine ecosystems, it will be able to estimate regional and global climate feedback processes. Considering human pressure on ecosystems, the project will study the processes in sensitive terrestrial, freshwater, coastal and marine areas of which some are hypothesised to be tipping elements in the climate system. This project enhances knowledge of the GHG dynamics in the ecosystems and link GHG in terrestrial, freshwater and marine ecosystems to provide a solid basis for estimation of regional and global climate feedback processes taking human pressure on ecosystems into account. It will study the processes in sensitive terrestrial, coastal and marine areas of which some are hypothesized to be tipping elements in the climate system. Thus, we will primarily focus on high latitude terrestrial systems, marine shelves and ocean areas and thereby advance the process-based representation of ecosystems in the EC-Earth Earth System Model. For this research project, we perform a large number of global EC-Earth greenhouse gas sensitivity experiments to explore the effect of the changing Arctic ecological systems as well as the change of physical constitutes such as global sea-ice cover retraction, differing snow covers in polar regions, leaching of GHG, etc, in the Earth's climate system from preindustrial(1850AD) to future climate scenarios (2100AD). To investigate this, we need to apply the EC-Earth model in its full-featured configuration including atmosphere, ocean, ocean biogeochemistry, land, interactive vegetation (LPJ), carbon cycle, land biogeochemistry, etc. In addition, we also need to perform simulations using for example single EC-Earth model components, such as the LPJ (the land ecosystem model, which itself runs on Tetralith and also uses the advantage of running in parallel requiring multiple cores and several nodes).