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Humble hut plays key role in climate change research

Taking the pulse: David Etheridge outside ‘‘Mabel’’ which houses equipment to collect data on the levels of carbon dioxide and other gases in the atmosphere.

Taking the pulse: David Etheridge outside ‘‘Mabel’’ which houses equipment to collect data on the levels of carbon dioxide and other gases in the atmosphere. Photo: Colin Cosier

It's easy to miss the old hut that stands behind Casey station on the Antarctic coastline.

The yellow shack, named ''Mabel'', is obscured by bigger, newer buildings, but the instruments inside play a far more significant role than its humble exterior might suggest. "It's measuring the pulse of the biosphere," says David Etheridge, a research scientist from CSIRO's marine and atmospheric research centre.

For the past decade the CSIRO has collected data on the levels of carbon dioxide and other gases in the atmosphere from three remote atmospheric monitoring stations, including Mabel, in Antarctica and the sub-Antarctic.

Crucial: Etheridge with measuring instruments.

Crucial: Etheridge with measuring instruments. Photo: Colin Cosier

"Without all the gases generated by cities and forests here we can measure the background levels of these chemicals in the atmosphere" Etheridge says.

It takes gas particles generated by the rest of the world about a year to migrate to the southern continent.

When combined with ice core data from Greenland and Antarctica, these measurements provide a picture of ongoing global distribution of carbon dioxide in the atmosphere over time.

One of the most important roles of these Antarctic stations is to show the difference in carbon concentrations between Cape Grim in Tasmania and the stations in Antarctica. The carbon dioxide drop between these two sites is the amount of gas absorbed by the world's largest carbon sink - the southern ocean.

About half the carbon dioxide released into the atmosphere by humans and natural sources is absorbed by oceans. Of this, the southern ocean stores just less than half.

While models suggest the southern ocean storage capacity should start losing its ability to absorb carbon dioxide because of climate change, the measurements to demonstrate this trend are difficult to obtain, Etheridge says.

The differences between the ocean reaching a tipping point and natural variability are so small that the performance of the instruments, including those at Casey, is crucial. "The entire surveillance of the southern ocean sink comes down to a calibration issue," he says. "And that's impossible to get funding for."

Since the 1990s, air captured in glass flasks and analysed for methane, carbon dioxide, nitrous oxide, carbon monoxide and hydrogen, are shipped or flown back to Etheridge's labs in Victoria for further analysis.

The instruments gather both continuous and periodic, every fortnight, samples, but the data from both methods can be contaminated.

"If the data isn't absolutely correct you could end up with false alarm," he says.

This issue has been hotly debated in academic journals for several years.

Etheridge says global measurements appeared to show a decreasing trend emerging from natural variability, but more data was needed to confirm this. "It's a bit of sitting and waiting."

Nicky Phillips and Colin Cosier travelled to Antarctica as part of the Australian Antarctic Division's media program.

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