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By Fiona Brown 29 July 2019 7 min read

Image: Richard Bennett

ACCURATE, reliable and comprehensive information about what is happening in our atmosphere is a critical piece of the puzzle if we are to mitigate and adapt to our changing climate. This information is being collected at highly-specialised stations strategically located around the world, including in Australia's own backyard. Well, that is if your backyard happens to be in remote Cape Grim in Tasmania, balmy Gunn Point in the Northern Territory, or the decks of the RV Investigator.

These stations form part of the World Meteorological Organisation’s (WMO) Global Atmosphere Watch (GAW) network, which encompasses over 500 stations from across more than 80 countries. Working together, the stations paint a detailed picture of the world’s atmosphere by measuring greenhouse and ozone depleting gases, reactive gases and aerosols in clean air environments. Air samples are analysed to determine both the composition and chemistry of our atmosphere and how it is changing over time, providing crucial information to help us best manage these changes and determine whether our actions are having the desired impact.

Measuring the world’s cleanest air

As far as clean air goes, you won’t find much cleaner than that at Cape Grim. Located in an isolated corner of the northwest tip of Tasmania, air arrives at Cape Grim after travelling long distances over the Southern Ocean under conditions described as ‘baseline’, meaning it remains unaffected by regional pollution sources (there are no nearby cities or industry to contaminate the air). This baseline air is representative of a large area of the Southern Hemisphere.

Cape Grim has been monitoring the composition of the atmosphere since 1976, with the first equipment being housed in an ex-NASA caravan. Since then, data collected at the station have been used in all five Intergovernmental Panel on Climate Change (IPCC) reports, all eleven international assessments of ozone depletion, and underpinned hundreds of research papers. Most recently, data from Cape Grim was used as part of an international project to determine the source of recent increases of ozone-depleting CFC-11 in the atmosphere.

The Cape Grim facility is one of only about 35 Global GAW stations, meaning it has been recognised as having a highly extensive and specialised measurement program. The station is jointly managed by CSIRO and the Bureau of Meteorology, with some of the collected data freely available online via CSIRO’s website.

“Cape Grim is considered one of the 3 premier stations in the WMO GAW network, primarily due to its pristine location in the mid-latitudes of the Southern Hemisphere (in the middle of the Roaring-Forties), and the comprehensive world-class measurement program that is undertaken there, including collaborations with multiple national and international organisations and universities. The long-term relationship between the Bureau of Meteorology and CSIRO is a real strength of the program,” says Paul Krummel, CSIRO's Cape Grim Lead Scientist.

Then and now. Above: Cape Grim in 1977, when monitoring equipment was housed in an ex-NASA caravan, which had to be permanently fixed to the ground to prevent high winds creating vibrations so large they could interrupt measurements. Below: Present day Cape Grim.

Monitoring the tropics

At the other end of Australia, forty kilometres northeast of Darwin on the Gunn Point peninsula, is the Northern Territory Baseline Air Pollution Station (aka NT BAPS). Established in 2010, NT BAPS is a relative new kid on the block, but thanks to its tropical location it is no less unique than Cape Grim.

As with its southern partner, NT BAPS provides high-quality year-round measurements of atmospheric composition under two very distinct meteorological regimes being the dry season (typically May to October) and the monsoon (November to April). But NT BAPS does so in the harshness of northern Australian where cyclones, extreme humidity, and high amounts of dust and smoke make taking air samples a challenge. High quality continuous measurements are made from two thermally insulated and temperature-controlled atmospheric laboratories, which enable dry-aerosol measurements to be taken even during the Wet season. This is the only such system in Australia, and one of only a few in the world.

NT BAPS is a Regional station within the WMO GAW program.

The NT BAPS is classed as a Regional station in the WMO GAW program. It provides important information about processes that influence the concentrations of air pollutants and greenhouse gases in northern Australia including fires, natural terrestrial and oceanic sources, regional development and long range transport from other regions.

As Zoe Loh, a research scientist with CSIRO’s Climate Science Centre, explains the location of NT BAPS makes it a particularly valuable member of the GAW network.

“Monitoring sites in the tropics are rare compared to those at higher latitudes, yet the tropics play a significant role in the global carbon cycle,” says Loh.

“NT BAPS is ideally placed to help us better understand the carbon pools that exist in the tropics and how they may be responding to a changing climate.”

NT BAPS is also unique in that the scientists are collaborating with the traditional owners of the land on which the station is located. Rangers from the Larrakia Nation Aboriginal Corporation collect flask samples and then send them off to CSIRO’s laboratory in Melbourne. There they are analysed along with other flask samples collected as part of CSIRO’s global flask network, which measures background atmospheric composition from a range of latitudes stretching from the South Pole at 90°S to Alert Station in the Canadian Arctic at 82°N.

“The Larrakia rangers are well skilled and already very active in the Gunn Point area conducting land and cultural heritage management activities, biodiversity surveys, and environmental monitoring, making them the perfect fit to provide local support for our work at NT BAPS,” says Loh.

All at sea

With no fixed address, Australia’s Marine National Facility’s Research Vessel (RV) Investigator may seem an unlikely candidate for inclusion in the GAW network, but this transient lifestyle is exactly what makes it such a valuable member.

Operated by CSIRO, RV Investigator was the first marine vessel, and thus the first mobile station, the WMO recognised as a regional station in its network. The Investigator has dedicated atmospheric composition measurement instruments on-board on a permanent basis, which means that whether the ship is in port, off the coast of Antarctica, or traversing the Great Barrier Reef the instruments are collecting data. The on-board research facilities include dedicated laboratories for air chemistry and the analysis of aerosol samples collected while at sea, along with a foremast fitted with a range of specifically designed inlets and other sensors. The vessel can also cater for range of other atmospheric research equipment as needed.

The RV Investigator was the first marine vessel recognised as part of the WMO GAW network.

By its nature and owing to its long-range capability, the RV Investigator is ideally suited for monitoring and characterising some of the most pristine and remote regions in the world, including those in the tropical Pacific, Indian and Southern Oceans. With a range of 10,800 nautical miles, and capable of 300 research days, the Investigator’s voyages span from the equator to the edge of the Antarctic ice. As such, it is able to monitor the boundary layer between air and ocean in inaccessible and under-sampled parts of the world.

“Seventy per cent of the Earth’s surface is covered by oceans,” says Ruhi Humphries, CSIRO Research Scientist leading the air monitoring research aboard RVI.

“Having world-class continuous measurements aboard a mobile platform, our own floating Cape Grim, has created a new era in atmospheric and climate science in the marine environment, and will really help us answer some important scientific questions."

The broader network

As can be seen through just these three Australian examples, the GAW network brings together a unique set of air pollution monitoring stations from around the world. In addition to the above, Australia’s CSIRO also oversees monitoring equipment located at Cape Ferguson, Queensland, on Macquarie Island, and at Casey and Mawson Research Stations in Antarctica; each which provide a unique perspective and contribution to our global picture of air pollution.

“The aim with our network of observing sites is to cover as much of the Australasian and Southern Ocean region as possible. This spans the tropics to the ice, and presents a range of unique and challenging environments for us to operate in. Our measurements provide us with a picture of the composition and chemistry of the atmosphere across much of the Southern Hemisphere and how these are changing with time. This information is essential for tracking the drivers of climate change and the effectiveness of any mitigation policies put in place to reduce emissions of the major climate drivers,” says Krummel.

The information that the GAW network of stations provides constitutes an essential contribution to our growing understanding of Earth’s climate system, including its variability and the way it is changing. Without this information, we would not know how our atmosphere has changed and how it is likely to change in the future. By working together, through international collaborations such as this, we are well-placed to tackle the challenge of managing our planet’s future climate.

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