This project involves a collaboration between the Scripps Institution of Oceanography (SIO) and the Climate Monitoring and Diagnostics Laboratory (CMDL) of the National Oceanic and Atmospheric Administration (NOAA) to create a single scale for reporting the concentration of atmospheric carbon dioxide (CO2) from the two laboratories so that the CO2 data can be compared without instrumental bias. Since 1956, SIO has maintained a global-scale program to measure the abundance of atmospheric CO2, calibrated with secondary standards using a constant-volume mercury-column manometer (CMM). From 1972 to 1995, the World Meteorological Organization designated SIO as the Central CO2 Laboratory for maintaining standard reference materials (SRM) for CO2 measurements worldwide. In 1995 this designation was transferred to CMDL. The calibration standards of the two institutions have not been reconciled since this transfer and this reconciliation is the focus of this effort. NOAA will support the CMDL part. The broader impacts of this work will be improved accuracy of several time-series measurements of atmospheric concentrations of carbon dioxide.
