NOAA Halocarbon Intercomparison Tanks Reach Australia and South Africa

September 21, 2005

Two sets of halocarbon gases in pressurized cylinders prepared by the NOAA/Climate Monitoring and Diagnostics Laboratory (CMDL), that form the core of the International HALocarbons in Air Comparison Experiment (IHALACE), reached research laboratories in South Africa and Australia in September (their furthest points south). The cylinders will return to NOAA/CMDL near the end of 2005 after having traveled the globe being measured by laboratories in the United States, Canada, Japan, South Africa, Netherlands, the United Kingdom, Germany, Switzerland, and Italy.


Halocarbons and other trace atmospheric gases contribute to climate forcing in addition to the major greenhouse gas, carbon dioxide. Many halocarbon gases are also involved in stratospheric ozone depletion and air quality. Worldwide measurements of these atmospheric trace gases are conducted by different groups reporting on different calibration scales. The IHALACE goal is to establish a calibration matrix that relates the calibration of each laboratory to one another. This will enable the construction of an integrated, global halocarbon database. The two sets of tanks will be checked for any potential drift in the calibration values when they return to CMDL. The sponsors of this international round robin are the Global Atmospheric Watch (GAW) program of the World Meteorological Organization (WMO), NOAA/CMDL, and the Upper Atmospheric Research Program of NASA.


There is no established international program for inter-laboratory comparison of halocarbon gases similar to that for carbon dioxide. The last successful halocarbon round robin was conducted in the mid 1970s. Recognizing this important gap, the Global Atmospheric Watch (GAW) program of the WMO and agencies responsible for major global networks organized the IHALACE with NOAA/CMDL responsible for preparing the standards and running the logistics of the intercomparison. This robin round supports the goals of the Earth Observations System ( by providing a common calibration scale for climatically important trace gases. The results of this intercomparison will be reported in the next Scientific Assessment of Ozone Depletion to be published in 2006. The Clean Air Act of 1990 requires NOAA and NASA to report an assessment of stratospheric ozone depletion once every four years to Congress.

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James W. Elkins