Tasmania’s Cape Grim Baseline Air Pollution Station program monitors the global atmosphere

The Earth’s climate is changing and the driving forces are the changes occurring in the composition of the planet’s atmosphere.

At the Kennaook/Cape Grim site in Tasmania, the Bureau of Meteorology operates a scientific observatory to measure the composition of the cleanest air in the world.

The station is on the west coast of Tasmania, near the northwestern tip – the location chosen because, when conditions are right, the air at Kennaook/Cape Grim has been carried in from the vast Southern Ocean, by through the frequently encountered westerly winds.

This air is representative of the “global” atmosphere, insensitive to local pollution.

Measurements recorded at Cape Grim provided the first evidence that photosynthetic phytoplankton are a source of gases that play a role in cloud formation.(Provided: BOM/Sam Cleland)

The Kennaook/Cape Grim science program is a collaboration between the office and CSIRO, with contributions from the Australian Nuclear Science and Technology Organization (ANSTO), the University of Wollongong and other groups around the world.

Image showing the location and range of the Cape Grim Air Monitoring Station sample.
Image showing the location and sampling range of the Cape Grim Air Monitoring Station in North West Tasmania.

The science program runs a team that chronicles the changing composition of the Earth’s atmosphere to inform Australia and the world about the key drivers of climate change.

From this air, the scientific team measures:

  • Greenhouse gases causing climate change
  • Substances that cause the hole in the ozone layer (stratospheric ozone depletion)
  • Other characteristics of the atmosphere that affect the climate, directly or indirectly.

Scientists around the world use data to understand the life cycle and impacts of various parts of the atmosphere, and how their influence changes over time.

The data also allows scientists to calculate emissions of harmful substances nationally and globally.

Instruments at an air monitoring station.
Along with stations at Mauna Loa in Hawaii and Alert in the Canadian Arctic, Cape Grim is one of the top three base air pollution stations in the world.(Provided: BOM/Sam Cleland)

Global monitoring of atmospheric composition

The Kennaook/Cape Grim Air Pollution Base Station and associated science program is guided by the World Meteorological Organization’s Global Atmosphere Monitoring Program.


The elements of atmospheric composition are measured at several sites around the world.

Few of them, and none in the southern hemisphere, do it as completely as in Kennaook/Cape Grim.

Data from this station is stored in global data centers coordinated by the Global Atmosphere Watch program.

A well-dressed man working inside a weather monitoring site.
An overview of the Cape Grim weather monitoring site in 1977.(Supplied: CSIRO)

Measure greenhouse gases

Greenhouse gas measurements began at this station in 1976. It started with carbon dioxide and various halocarbons, which are potent man-made greenhouse gases.

Carbon dioxide at that time was recorded at 330 parts per million (ppm). Almost half a century later, it has increased by around 25%.

The station’s work now captures all major greenhouse gases, including:

  • Carbon dioxide, CO2
  • Methane, CH4
  • Nitrous oxide, N20

It also includes synthetic gases such as:

  • Chlorofluorocarbons (CFCs)
  • Hydrochlorofluorocarbons (HCFCs)
  • Hydrofluorocarbons (HFCs)
  • Perfluorocarbons (PFCs)
  • Sulfur hexafluoride (SF6)
Cape Grim Air Monitoring Station in North West Tasmania in 1977.
In 1976, the first Cape Grim equipment was installed in an ex-NASA trailer, which had to be anchored to the ground due to high winds.

Ozone Depleting Substances Monitoring

Ozone in Earth’s stratosphere protects our planet from some of the strongest solar radiation.


Ozone depleting substances are chemicals that destroy ozone in the stratosphere. These gases are responsible for the hole in the ozone layer. Many of them are also powerful greenhouse gases.

Concerns about the impact of these chemicals led to the Vienna Convention for the Protection of the Ozone Layer in 1985.

This was followed by the Montreal Protocol on Substances that Deplete the Ozone Layer in 1987.

The Montreal Protocol sought to curb production and called for continued monitoring of these chemicals in the atmosphere. The Kennaook/Cape Grim measures enable Australia to meet some of these monitoring requirements.

The station’s science team regularly measures all ozone-depleting substances.

This is possible thanks to a collaboration with the international network AGAGE (Advanced Global Atmospheric Gases Experimental).

Man handling large metal bottles inside a room.
The Cape Grim Air Archive began in 1978 as a means of preserving Cape Grim’s “basic” clean air for future science.(Supplied: CSIRO)

Other Measures at Kennaook/Cap Grim

Measurements of greenhouse gases and ozone-depleting substances are an important part of the work at Kennaook/Cape Grim, but there is much more.

The composition of the Earth’s atmosphere is changing in complex and subtle ways.

These changes influence how the atmosphere and climate respond. For example:

  • Atmospheric particles can influence how sunlight passes through the atmosphere. Particles are also essential for cloud formation
  • Reactive gases such as nitric oxides and ozone influence the chemistry of the atmosphere. They also participate in the formation of particles
  • Radon measurements indicate if the air being measured has recently been above ground, therefore works as a tracer
Cap Grim air measurement station
Kennaook is the traditional Aboriginal name for the Cape Grim site.(ABC News: Sarah Clarke)

The science team takes detailed and precise measurements of these and more. This makes it possible to chronicle the influence of all these factors and to understand the changes over time.

The office and CSIRO, along with contributions from the Australian Nuclear Science and Technology Organization (ANSTO) and the University of Wollongong, have chronicled the changing composition of the global atmosphere, through their work in Kennaook/Cap Grim, since 1976.

The work continues.

More information can be found on CSIRO’s Cape Grim Data website.

Sam Cleland is the Officer in Charge of the Kennaook/Cape Grim Air Pollution Base Station

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