Salt marshes are highly dynamic ecosystems in the transition zone between marine and terrestrial environments and are characterised by a complex interplay of abiotic and biotic factors. They are recognised for their high potential for ecosystem services due to high CO2 sequestration rates and at the same time rather low CH4 and N2 O emissions. Here, we present a world-unique ecosystem warming field experiment installed at the salt marshes of Hamburger Hallig in the national park Schleswig- Holstein Wadden Sea. The effect of above- and belowground warming on the interactions of plants, soils, soil organisms and in turn ecosystem functions is studied considering the full elevational gradient from pioneer, via low to high marsh communities, where temperature is controlled but all other abiotic and biotic factors represent the natural environment. Experimental plots are established in each of the three salt marsh zones, which differ in inundation frequency. Every plot is subjected to one of three warming treatments including a +1.5 °C and a +3.0 °C experimental warming, as well as a control treatment with ambient temperature. The warming plots are actively heated belowground with heating cables. Every plot is equipped with a dome-shaped greenhouse for passive aboveground heating. Different levels of heating are achieved using different amounts of greenhouse foil. A closed chamber approach combined with in situ-measurements of greenhouse gases using a portable Fourier transformation infrared absorption spectrometer (DX4015, Gasmet) allows the determination of altered CO2 , CH4 , and N2 O fluxes introduced by changes of marsh vegetation productivity and shifts in soil fauna community due to enhanced temperature. Additionally, CO2 concentrations will be measured in top soil pore space by permanently installed sensors. To investigate, how warming affects soil´s redox state, possibly promoted by enhanced soil respiration and thereby increased O2 consumption, electrodes will be installed at different depths allowing measurements of soil redox potentials. Altogether, the described approach will promote an understanding of warming effects on critical ecosystem functions in terms of greenhouse gas fluxes. This is crucial in order to comprehend plant-soil feedbacks and other complex ecosystem processes such as biogeochemical element cycles influenced by the on-going global warming.