Once estimated, the GNSS-based tropospheric delays can then be used for climate applications. Indeed, GNSS measurements are delayed by the precense of water vapour along the signal propagation path. This water vapour is tightly coupled to processes like energy transfer and precipitation and is the major greenhouse gas present in the Earth's atmosphere. Water vapour plays thus an important role in climate models and in the global warming process.

Using measurements of the surface air pressure and temperature, the tropospheric delays estimated from GNSS observations can be converted into Integrated (column) Water Vapour (IWV). This IWV obtained from homogeneously reprocessed GNSS-based tropopsheric delays over the last 15+ years can then be used to study the climate variability and for climate change monitoring.