General Comments

GMD carbon cycle data are freely available directly from NOAA and from the CDIAC and WMO WDCGG data archive centers. Before actual data are made available, they must undergo critical evaluation. Evaluation procedures ensure that (1) the standard reference gases used in making the measurements in Boulder and in the field are well characterized (i.e., calibrated before and after their use); (2) samples compromised during collection or analysis are identified, and (3) valid samples not representative of typical background conditions are identified. Quality control of the data requires considerable time and effort and is an essential part of the GMD operations.

Warning: Preliminary data include the this group's most up-to-date data and have not yet been subjected to rigorous quality assurance procedures. Preliminary data viewed from this site are "pre-filtered" using tools designed to identify suspect values. Filtering is performed each time a data set containing preliminary data is requested. Filtering, however, cannot identify systematic experimental errors and will not be used in place of existing data assurance procedures. Thus, there exists the potential to make available preliminary data with systematic biases. In all graphs, preliminary data are clearly identified. Users are strongly encouraged to contact Dr. Pieter Tans, Group Chief ( before attempting to interpret preliminary data.

Learn more about GMD carbon cycle measurements from the Global Greenhouse Gas Reference Network web site.