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The CCGG cooperative air sampling network effort began in 1967 at Niwot Ridge, Colorado. Today, the network is an international effort which includes regular discrete samples from the NOAA ESRL/GML baseline observatories, cooperative fixed sites, and commercial ships. Air samples are collected approximately weekly from a globally distributed network of sites. Samples are analyzed for Carbon Dioxide (CO2), Methane (CH4), Carbon Monoxide (CO), Hydrogen Gas (H2), Nitrous Oxide (N2O), and Sulfur Hexafluoride (SF6); and by INSTAAR for the stable isotopes of CO2 and CH4 and for many volatile organic compounds (VOC) such as ethane (C2H6), ethylene (C2H4) and propane (C3H8). Measurement data are used to identify long-term trends, seasonal variability, and spatial distribution of carbon cycle gases. 

Abstract Molecular hydrogen (H₂) is an abundant and reactive constituent of Earth's atmosphere, with links to climate and air quality. Anthropogenic emissions of H₂are expected to rise as the use of H₂as an energy source increases. Documenting past variations in atmospheric H₂will help to validate current understanding of the global H₂budget. The modern instrumental record begins in the 1980s; there is little information about atmospheric H₂prior to that time. Here, we use firn air measurements from a 2001 South Pole campaign to reconstruct atmospheric H₂levels over the 20th century. Inversion of the measurements indicates that H₂over South Pole has increased from 350–540 ppb from 1910–2000. A biogeochemical box model indicates that the atmospheric burden of H₂increased by 37% over that time. The rise in H₂is consistent with increasing H₂emissions from fossil fuel combustion and increasing atmospheric production from methane oxidation.