VLBI for climate studies (FWF P16992‐N10) The atmosphere, in particular the lowest atmospheric layer, the troposphere, contributes significantly to the uncertainty of space‐geodetic techniques observing at radio wavelengths. One of those techniques, Very Long Baseline Interferometry (VLBI), already started its observations in the seventies and continued operations without major changes of the measurement process until today. Thus, different from other space‐geodetic techniques, VLBI is able to provide stable and homogeneous series of observational data almost reaching the length of a climate normal period of 30 years at some sites. Today, technical developments and improved tropospheric models allow determining tropospheric parameters by the analysis of VLBI data. Within project “VLBI for climate studies” global variations of atmospheric water vapor, one of the most important climate parameters could be assessed. Within the frame of the project the operational provision of combined long time‐series of tropospheric parameters was successfully introduced within the IVS (International VLBI Service for Geodesy and Astrometry). Considering the unevenly sampled characteristics of the observations with specific mathematical methods, it was possible to obtain significant long‐term trends of atmospheric water vapor at some VLBI sites. The results show a global increase in water vapor and correspondingly the humidity above the VLBI stations during the last 25 to 20 years. However, at some sites, e. g. Hartebeesthoek, South Africa, atmospheric water vapor decreases. The combined time‐series of tropospheric parameters were compared to results of the IGS (International GNSS Service) and to the ERA‐40 reanalysis data‐set, a numerical weather model of the ECMWF (European Centre for Medium‐Range Weather Forecasts). In general, long‐term trends derived by the various techniques agree well. However, disagreements at some sites, e. g. at Fortaleza, Brazil, reveal discrepancies between observed values and the ECMWF reanalysis model and might point out inconsistencies present in the numerical weather model. During the project the second global VLBI solution worldwide using OCCAM 6.1 and DOGS‐CS 4.05 could be established. Austria’s participation within IVS was significantly strengthened and a contribution to global climate change studies was achieved.