The latest greenhouse gas (GHG) data updated monthly from one of the cleanest air sources in the world.

Cape Grim Baseline Air Pollution Station

Cape Grim, on Tasmania’s west coast, is one of the three premier Baseline Air Pollution Stations in the World Meteorological Organization-Global Atmosphere Watch (WMO-GAW) network. Baseline stations are defined by the WMO to meet a specific set of criteria for measuring greenhouse and ozone depleting gases and aerosols in clean air environments.

The Cape Grim station is positioned just south of the isolated north-west tip (Woolnorth Point) of Tasmania. It is in an important site, as the air sampled arrives at Cape Grim after long trajectories over the Southern Ocean, under conditions described as ‘baseline’. This baseline air is representative of a large area of the Southern Hemisphere, unaffected by regional pollution sources (there are no nearby cities or industry that would contaminate the air quality).

Cape Grim is a joint responsibility of the Bureau of Meteorology and the Commonwealth Scientific and Industrial Research Organisation (CSIRO). The Bureau of Meteorology funds and operates the Cape Grim atmospheric observational facility. CSIRO analyses and models the resultant data, which are made available to interested parties – Australian government agencies, industry, the public and international agencies.

Most GHGs (for example carbon dioxide, nitrous oxide, HFCs, PFCs, sulfur hexafluoride) have shown continuous increases in concentration since the mid-to-late 1970s. The growth of some GHGs (for example methane) has slowed recently and some are in decline (CFCs and halons for example).

Cape Grim Baseline Air Pollution Station

Changes in the air

Dry air is composed of nitrogen (78 per cent), oxygen (21per cent) and other gases, such as argon, carbon dioxide, methane, hydrogen, nitrous oxide etc, which make up the remaining one per cent.

Dr Ray Langenfelds with the Cape Grim air sample archive.

Carbon dioxide is measured in parts per million molar (ppm) – the 2013 global mean carbon dioxide level was 395 ppm. If you have a sample of dry air, made up of one million molecules, 395 would be carbon dioxide molecules. Carbon dioxide concentrations in the air were reasonably stable (typically quoted as 278 ppm) before industrialisation (in the timeframe of human existence). Since industrialisation (typically measured from the mid-18th century), carbon dioxide concentrations have increased by about 40 per cent, based on measurements from Cape Grim and on air samples collected from Antarctic ice at Law Dome.

Since industrialisation, methane concentrations have increased by more than 150 per cent to present day values.

Nitrous oxide concentrations in the air were reasonably stable before industrialisation (in the timeframe of human existence), typically quoted as 270 ppb (parts per billion molar). Since industrialisation, nitrous oxide concentrations have increased by about 20 per cent to present day values.

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