We propose to initialise a European Network for observations of molecular Hydrogen and to put in place a new and consistent calibration scale for molecular Hydrogen. The observational network will have 12 continuous measurements sites in Europe, 7 flask-sampling sites in Europe and 6 global flask-sampling sites. Concerning the European sites, a range of observation from clean air stations for measurements of atmospheric background to moderately polluted (e.g. urban outflow) and urban (i.e. polluted) sites was chosen.

This will enable to improve the understanding of hydrogen in the global background atmosphere and of the impact of European emissions on the present day atmosphere, e.g. using local modelling techniques and radon flux calculations. We further propose to perform budget studies of molecular hydrogen (on a global and regional scale) and to study sinks and sources. Especially the important soil sink will be studied (mechanistically and experimentally).

A first systematic study of isotopic composition of molecular hydrogen in the atmosphere is proposed, using observations from global and European flask sampling sites and global models, which hydrogen isotope fractionation processes will be incorporated. Global and regional models will be used to investigate the budget of atmospheric hydrogen, by comparing mixing ratios and isotope ratios between model and observations and by varying underlying model emission patterns.

The Proposal further includes some studies to assess the impact of atmospheric hydrogen on the present day atmosphere, i.e. the influence on the oxidation capacity of the troposphere, the lifetimes of greenhouse gases like CH4 and on the stratospheric budgets of water vapour and ozone. Some exploratory studies will be carried out to investigate these impacts under changed atmospheric hydrogen levels, associated with the use of hydrogen as a carrier of economy.