Lead Investigator(s):

Pieter Tans
Thomas J. Conway

MLO Contacts(s):

Aidan Colton
808-933-6965 (x233)
Paul Fukumura
808-933-6965 (x223)

Web Site(s):


Date Started:


Related Programs

In Situ Carbon Monoxide
In Situ Carbon Dioxide
In Situ Methane
Greenhouse Gases


Flask sampling box
Flask sampling box
Analysis Equipment in Boulder
Analysis equipment in
Boulder, CO


NOAA logo National Oceanic and Atmospheric Administration (NOAA),
Earth System Research Laboratory (ESRL)

What does this program measure?

The NOAA CMDL CCGG cooperative global air sampling network is an international effort, and includes regular discrete air flask samples from both Mauna Loa Observatory and Cape Kumukahi, Hawaii. Complete information about the program is available at http://www.esrl.noaa.gov/gmd/ccgg/flask.html.

The program measures the following (where ppm is parts-per-million, ppb is parts-per-billion, ppt is parts-per-trillion, pm is per-million, and per mil is per-thousand):

Chemical Formula
Carbon Dioxide
Carbon Monoxide
H 2
Nitrous Oxide
Sulfur Hexaflouride
isotopic ratio of carbon dioxide
Carbon-13 / Carbon-12
per mil
isotopic ratio of carbon dioxide
Oxygen-18 / Oxygen-16
per mil

How does this program work?

Flask samples are taken at Mauna Loa Observatory and Cape Kumukahi, Hawaii, and are sent to the NOAA ESRL GMD laboratory in Boulder, Colorado. They are then analyzed with the following techniques:

  • Carbon dioxide (CO2) is measured by nondispersive infrared absorption;
  • Methane (CH4) is measured by gas chromatography (GC) with flame ionization detection;
  • Carbon monoxide (CO) is measured by GC with mercuric oxide (HgO) reduction detection;
  • Hydrogen (H2) is also measured by GC with HgO detection;
  • Nitrous Oxide (N2O) and sulphur hexafluoride (SF6) use GC with electron capture detection;
  • Carbon-13 (13C) / Carbon-12 (12C) and isotopes 18O / 16O use mass spectrometry.

Why is this research important?

In order to determine temporal and spatial variations in the global atmosphere, deduce better estimates of sources and sinks, and better understand the carbon cycle.

Are there any trends in the data?

Carbon dioxide is increasing by ~1.5 parts per million per year;

Global Carbon Dioxide including MLO data
Methane was increasing, but has been nearly constant for the past 2 years;

Global Methane with MLO data in red
Nitrous oxide and sulphur hexaflouride are increasing. Sulfur hexaflouride (SF6) is the most potent greenhouse gas on a molecule-to-molecule basis, and has an atmospheric lifetime of about 3,000 years! But, since SF6 concentrations are relatively low at present, their greenhouse effet will not be felt for many years. SF6 is used in the electrical power transmission industry and its sources are mainly in the northern hemisphere.

Global SF6

Carbon-13 / Carbon-12 is decreasing.

How does this program fit into the big picture?

What is it's role in global climate change?

The CCGG flask sample network consists of the sites shown on the map below (click map to enlarge).


Carbon dioxide is the most important anthropogenic “greenhouse gas” (it produces about 60% of present day greenhouse gas climate forcing), followed by methane (about 20%). Nitrous oxide and sulphur hexaflouride are also infrared absorbers. Carbon monoxide affects the greenhouse gases through its atmospheric chemistry. A better understanding of the carbon cycle is crucial to make informed decisions about future climate and energy policies.

Comments and References

More information, plus many figures, are available from the CCGG web site.