The International Committee for Weights and Measures (CIPM) and the World Meteorological Organization (WMO), recognizing the need for standardized, accurate and reliable data in the fields of meteorology, hydrology and other related geophysical sciences, have agreed to work together to ensure that data related in particular to measurements of state and composition of atmosphere and water resources, coming from the programmes organized under the auspices of the WMO, are properly based on units traceable to the SI through the procedures of the CIPM MRA and the Technical Regulations of the WMO.