In 1972 NOAA created the Geophysical Monitoring for Climatic Change (GMCC) program. Over the years GMCC has evolved to what is now the Global Monitoring Laboratory (GML). The initial focus of GMCC was maintaining long-term measurements at NOAA’s four Atmospheric Baseline Observatories and several regional sampling sites.

Over time and with support from partners, GML has established and operated many other sites which have developed into global and regional observing networks focused on different aspects of the atmosphere as they relate to stratospheric ozone and climate change. From its inception in 1972 GML and its predecessors have also used intensive field campaigns to better understand and explain the long-term observations from each of these networks with new instrument advances and enhanced spatial and temporal sampling.

All GML data are archived for scientists, policymakers and the public to freely access. The data have clearly defined quality control and standard operating procedures to ensure measurements are tied to common and traceable standards. These data are intended to capture changes in the Earth’s atmosphere and its climate and to support atmospheric and climate data analyses, satellite observation validations and improvements in model development and predictions.

Observation Networks

The Global Greenhouse Gas Reference Network

NOAA measurements of carbon dioxide began in 1967 with discrete air samples from Niwot Ridge, CO and with continuous in-situ measurements starting in the early 1970's at the Atmospheric Baseline Observatories. The number of flask air sampling sites expanded in the 1980's to ~50 sites in mostly remote locations around the world, and measurements of additional long-lived greenhouse gases (GHG) were added. In the mid 2000s, GML expanded flask sampling and GHG in-situ measurements to towers and from aircraft over North America. In recent years, GML has developed a technique for balloon-borne sampling of the atmospheric column for GHGs. These data are critical for monitoring, mapping and understanding GHGs distributions from regional to global-scales.

The Halocarbons and other Trace Species Network

NOAA measurements of chlorofluorocarbons and other ozone-depleting substances began in the late 1970s with weekly flask samples at five remote sites. In the 1980s flask sampling was expanded to eleven sites, and in situ measurements were added at five sites. In the early 1990s and thereafter the number of gases measured in flasks was significantly expanded (now over 60). The current flask network consists of 10 background sites and 6 non-background sites. In addition, the HATS network collaborates with the GGGRN to measure air samples from light aircraft and tall towers with a North American focus.

Surface Radiation

NOAA measurements of high quality surface radiation began at the Observatories starting with transmission of direct solar radiation at Mauna Loa in 1958; it currently consists of 5 global sites. The U.S. surface radiation budget (SURFRAD) network began operations in 1995 and expanded to six sites by 2003 with additional atmospheric observations. While SOLRAD has a long history in NOAA, GML has monitored surface radiation at six urban SOLRAD stations since 2002. An Antarctic ultraviolet and ozone monitoring network established in 1987 by NSF in response to serious ozone depletion in Antarctica was transitioned to GML in 2010. The NOAA Brewer Spectrophotometer (NEUBrew) Network began in 2006 and consists of six U.S. stations measuring ozone and spectral UV radiation. More recently, several mobile SURFRAD stations have been developed for short-term regional process studies. Working with U.S. and international partners, broadband and UV calibration facilities are hosted by GML.

NOAA Federated Aerosol Network

NOAA measurements of aerosol number concentrations started at the Atmospheric Baseline Observatories in the mid 1970s. A few years later measurements were expanded to include aerosol light scattering (late 1970s) and, eventually, aerosol light absorption (1990s). In the 1990s GML also began conducting measurements at less remote sites. Today, GML operates aerosol instrumentation at three NOAA Observatories as well as Summit, Greenland and continues to share expertise and provide support to the international NOAA Federated Aerosol Network, which now comprises over 30 cooperative sites distributed worldwide.


Ozone total column measurements started at Caribou, ME, Bismarck, ND, and Nashville, TN, and at the Mauna Loa and South Pole Observatories in early 1960s. Today GML operates total column ozone instruments (Dobson) at the 4 Atmospheric Baseline Observatories and at 11 other stations around the world. GML started continuous surface ozone measurements and routine ozone vertical profiling up to 30km altitude at the 4 observatories in the 1970s and 1980s respectively. The 16 surface ozone network sites and 8 ozonesonde network sites are strategically located at selected geophysical locations with a purpose to sample the background atmosphere representative of regional and/or global processes.

Water Vapor

NOAA’s balloon-borne in-situ measurements of water vapor vertical profiles from the surface to the middle stratosphere began at Boulder in 1980. In 2004, a second water vapor sounding site was established at Lauder, New Zealand. Hilo, Hawaii, was added as a third water vapor site in 2010. GMLs three water vapor sounding sites are affiliated with several multinational monitoring networks.

Field Campaigns

To better understand processes driving the global distributions of trace gases, aerosols and radiation observed by the GML networks, the GML has a long history of participating in short-term ground, aircraft and balloon-based studies. These studies bring together expertise from universities and other governmental and non-governmental institutions and have often led to significant advancements in measurement techniques.