Recommendation 1 of the 18th CCPR (2005)

On the importance of SI traceable measurements to monitor climate change

The Consultative Committee for Photometry and Radiometry (CCPR),

recalling Resolution 4 of the 21st General Conference on Weights and Measures (1999) concerning the need to use SI units in studies of Earth resources, the environment, human well-being and related issues,


  • the increasing importance of optical radiation based measurements from ground, air and space which support research into the understanding of the causes and impacts of climate change;
  • the cooperation between the World Meteorological Organization (WMO), the International Bureau of Weights and Measures (BIPM) and the CCPR, relating to the metrological needs of the WMO;
  • the difficulty of demonstrating and maintaining traceability to the International System of Units (SI) in the space environment and because the levels of accuracy needed are often more demanding than those needed to satisfy current industrial requirements;
  • the particular need for space-based experiments to be traceable to SI units and the difficulty of obtaining a calibration during the operational phase of a mission;

strongly recommends relevant bodies to take steps to ensure that all measurements used to make observations which may be used for climate studies are made fully traceable to SI units;

and further recommends appropriate funding bodies to support the development of techniques which can make possible a set of SI-traceable radiometric standards and instruments to allow such traceability to be established in space.

reference The reader should note that the official version of this Resolution is the French text

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