The Global Greenhouse Gas Reference Network for the Carbon Cycle and Greenhouse Gases (CCGG) Group is part of NOAA'S Earth System Research Laboratory (ESRL) in Boulder, CO. The Reference Network measures the atmospheric distribution and trends of the three main long-term drivers of climate change, carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), as well as carbon monoxide (CO) which is an important indicator of air pollution. The Reference Network measurement program includes continuous in-situ measurements at 4 baseline observatories (global background sites) and 8 tall towers, as well as flask-air samples collected by volunteers at over 50 additional regional background sites and from small aircraft. The air samples are returned to ESRL for analysis where measurements of about 55 trace gases are done. NOAA's Global Greenhouse Gas Reference Network maintains the World Meteorological Organization international calibration scales for CO2, CH4, CO, N2O, and SF6 in air. The measurements of the Global Greenhouse Gas Reference Network serve as a comparison with measurements made by many other international laboratories, and with regional studies. They are widely used in studies inferring space-time patterns of emissions and removals of greenhouse gases that are optimally consistent with the atmospheric observations. They serve as an early warning for climate "surprises". The measurements are also helpful for the ongoing evaluation of remote sensing technologies.

Aircraft Program Measurements: Since its inception in 1992, the Global Greenhouse Gas Reference Network's aircraft program has been dedicated to collecting air samples in vertical profiles over North America. The program's mission is to capture seasonal and inter-annual changes in trace gas mixing ratios throughout the boundary layer and free troposphere. Data collected by the aircraft program provide a view of how the large-scale horizontal and vertical distribution of the measured trace gases change throughout a given year over the continent. The measured data are baseline levels, trends, and causes of variability of atmospheric gases that have the potential to affect global climate.

The historical data set contains measurements from 31 aircraft program missions. The ongoing data set is contingent upon the aircraft program missions that are still in use going forward. At present, most aircraft program flights collect 12 flask samples at different altitudes via a portable, automated sampling system. At a predetermined altitude, the sampling system is simply activated by a toggle switch that is easily accessible to the pilot. Time, location and auxiliary variables such as temperature and relative humidity are logged with each sample and downloaded into the NOAA/ESRL database when the samples are returned to the laboratory. Sampling frequency and height distribution varies at each site, but samples are collected from 500 m above ground to 8000 m above sea level at the majority of aircraft sites. While sampling flights have been conducted at some sites as often as two to three times per week, sample flights at most sites are only carried out once every two to three weeks.

Through the Big Earth Data Initiative (BEDI), ESRL/GMD has taken their data collection and converted files into NetCDF-4, a self-describing format.