- NOAA/CMDL Baseline Observatories
- Cooperative Sampling Sites
- (ALT) Alert, N.W.T.
- (ASC) Ascension Island, Atlantic Ocean
- (ASK) Assekrem, Algeria
- (AZR) Terceira Island, Azores
- (BAL) Baltic Sea
- (BME) St. David's Head, Bermuda
- (BMW) Southhampton, Bermuda
- (BSC) Black Sea
- (CBA) Cold Bay, Alaska
- (CGO) Cape Grim, Tasmania
- (CHR) Christmas Island, Pacific Ocean
- (CRZ) Crozet, Indian Ocean
- (EIC) Easter Island, Pacific Ocean
- (GMI) Guam, Mariana Islands
- (GOZ) Dwejra Point, Gozo
- (HBA) Halley Bay, Antarctica
- (HUN) Hegyhatsal, Hungary
- (ICE) Heimaey, Vestmannaeyjar, Iceland
- (IZO) Tenerife, Canary Islands
- (KCO) Kaashidhoo Climate Observatory, Republic of Maldives
- (KEY) Key Biscayne, Florida
- (KUM) Cape Kumukahi, Hawaii
- (KZD) Sary Taukum, Kazakhstan
- (KZM) Assy Plateau, Kazakhstan
- (MHT) Mace Head, Count Galway, Ireland
- (MID) Sand Island, Midway
- (NMB) Gobabeb, Namibia
- (NWR) Niwot Ridge, Colorado
- (PSA) Palmer Station, Antarctica
- (PTA) Point Arena, California
- (QPC) Qinghai Province, China
- (RPB) Ragged Point, Barbados
- (SEY) Mahe Island, Seychelles
- (SHM) Shemya Island, Alaska
- (STM) Station M, Atlantic Ocean
- (SUM) Summit, Greenland
- (SYO) Syowa Station, Antarctica
- (TAP) Tae-ahn Peninsula, South Korea
- (TDF) Tierra Del Fuego, Argentina
- (UTA) Wendover, Utah
- (UUM) Ulaan Uul, Mongolia
- (WIS) Sede Boker (Negev Desert)
- (ZEP) Ny-Alesund, Spitsvergen, Svalbard
- Shipboard Sampling
- Tall Tower Sampling
- Discontinued Sites
- Amsterdam Island, Indian Ocean
- St. Croix, Virgin Islands
- Terceira Island, Azores
- (CMO) Cape Meares, Oregon
- Cosmos, Peru
- Falkland Islands, Atlantic Ocean
- (ITN) Grifton, North Carolina
- Kitt Peak, Arizona
- McMurdo Station, Antarctica
- Mauna Kea, Hawaii
- Mould Bay, N.W.T., Canada
- Kaitorete Spit, New Zealand
- Olympic Peninsula, Washington
- Point Six Mountain, Montana
- Scripps Institution of Oceanography, La Jolla California
- Station 'C', Atlantic Ocean
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