Condition

There have been subtle but significant changes to the Earth's atmosphere that have become apparent in recent decades. For example, the concentration of carbon dioxide gas has been rising steadily, and the average temperature of the atmosphere is greater now than it has been for a long time.

The building up of knowledge about various atmospheric processes has highlighted the role of the Greenhouse Effect. In recent years, the modifications to this, know as the Enhanced Greenhouse Effect, has been acknowledged and the changes have become increasingly apparent.

Through its various monitoring programs, the station at Cape Grim has been providing valuable data that has been crucial to gaining a better understanding of these effects, and for atmospheric processes in general.

Pressure

There are many different scenarios for how the Earth's climate may change depending on the amount of change in the concentration of the various greenhouse gases, and how mitigating factors such as increased humidity and particulates are affected.

One of the great difficulties in determining possible changes to the climate is not having a complete understanding of the whole atmospheric system, and in particular, the interaction between the various components. Computer models have been developed to assess possible changes under a variety of different climate change scenarios. The models rely on a good understanding of atmospheric processes, and without this their results are less accurate.

To get the information to better understand the way the atmosphere works, an extensive and coordinated world-wide monitoring program was required. It was very difficult finding sites that were both accessible, but could also monitor background air that was not 'polluted' by local sources. It's position in the path of the prevailing westerly winds of the Southern Ocean meant that Tasmania was well placed to site one of the stations.

Response

To obtain a better understanding of the way the atmosphere was changing, the World Meteorological Organisation started the Background Air Pollution Monitoring Network in 1972. It was designed to collect and test background, or 'baseline', air from sites around the world. The program is now known as Global Atmosphere Watch.

Sites were chosen in remote areas to minimise contamination from local sources. Cape Grim in north-west Tasmania was chosen for studying air in the southern hemisphere. Set up in 1976 on the Woolnorth property, the first laboratory was a caravan donated by NASA. A permanent building that was purpose-built soon after is now a highly sophisticated facility providing essential data on the southern hemisphere atmosphere.

The station is funded and managed by the Bureau of Meteorology, which jointly supervises the scientific program with the CSIRO Division of Atmospheric Research. Monitoring of the highest quality is the goal. Samples are regularly sent to other laboratories around the world to ensure accuracy, as well as to participate in a range of cooperative programs. The air of most interest is that originating from the Southern Ocean-the baseline air. However, the Station also conducts monitoring of non-baseline air in order to study dust transport from mainland Australia, urban air pollution plumes from Victoria and South Australia and emissions from Tasmania. Measurements include the types and amount of gases and particles in the air (e.g. carbon dioxide, radon, aerosols), of solar radiation (e.g. intensity, ultraviolet levels) and of meteorological conditions (e.g. wind speed and direction, rainfall, temperature, pressure). Sampling is carefully controlled to avoid local sources of pollution from around the Cape Grim station. In addition, the site itself is closed to general visitors in order to further reduce the likelihood of contamination.

Other research studies at Cape Grim include ozone depleting chemicals; urban air pollution, and natural sources of trace chemicals in the air as well as climate change and variability.

The work conducted at Cape Grim is crucial to a greater understanding of the nature and behavior of the atmosphere. It is the most sophisticated station in the southern hemisphere, so is an important link in the global network of monitoring stations that is helping to measure and explain changes in the atmosphere.

Acknowledgment

Adapted from Holper 1992 and the Bureau of Meteorology. Advice was also provided by Dr Neil Tindale, Senior Research Scientist/Officer in Charge, Cape Grim Baseline Air Pollution Station.