The cleanest air in the world is at Tasmania's Kennaook/Cape Grim. It's helping solve a climate puzzle

The Kennaook/Cape Grim baseline air-monitoring station sits on Tasmania’s north-west coast. (ABC News: Jordan Young)

When the “roaring forties” blow in from the Southern Ocean, Jamie Oliver knows he’s in for a rough time.

“Sometimes in the winter, when it gets wet and cold for days and days, you get a bit sick of it,” the 55-year-old beef farmer admits.

But Mr Oliver, who’s lived on Tasmania’s north-west coast since he was a teenager, wouldn’t want to be anywhere else.

“It’s a magnificent place,” he said.

“The air, I don’t know if it’s just me, but it’s so crisp and clean. And you feel like you can breathe it properly.”

His assessment about the region’s air quality is backed up by decades of science.

Twenty-five kilometres up the coast from his property is one of the world’s three “premier” stations that monitor baseline air pollution.

Established in 1976, the Kennaook/Cape Grim facility can accurately measure changes in the global atmosphere without the interference of local contamination.

“Air here under baseline conditions is very, very clean,” CSIRO atmospheric scientist Melita Keywood said.

“It’s 1,000 times cleaner in terms of the number of particles than we would measure in Melbourne, for example – and that’s Melbourne on a good day.”

Air archive reflects human impact on global atmosphere

On a rooftop deck overlooking the rugged coastline, the facility’s officer-in-charge, Sarah Prior, is checking the direction of the wind.

When it comes from the west or south-west, it’s travelled thousands of kilometres across the Southern Ocean, avoiding the smog and dust of cities or landmasses.

“At that time … we are measuring the lowest levels of pollution that you’ll see,” Ms Prior said.

Scientists at Kennaook/Cape Grim describe it as “baseline” air — the cleanest on the planet.

Once it’s captured, the air is siphoned into a laboratory where high-tech machines analyse its chemical and physical properties.

“In a nutshell, we measure our greenhouse gases and ozone-depleting substances,” Ms Prior said.

“We also measure the aerosols and reactive gases, and we measure radon as well.”

Air quality readings taken over 50 years

For almost five decades, the station has been pivotal in tracking the impact of human activity on the atmosphere.

When the first readings were taken at Kennaook/Cape Grim, carbon dioxide levels were just below 330 parts per million.

These days they are at more than 417 parts per million, an increase of almost 25 per cent since the 1970s.

“The record here is showing that we are having an influence on the CO2 in the atmosphere, which is contributing to climate warming,” Dr Keywood said.

The increase in carbon dioxide, as well as other greenhouse gases and chemicals, is reflected in Kennaook/Cape Grim’s “archive” of air.

Every two months, staff at the facility don protective gear to cryogenically fill a high-pressure tank with thousands of litres of baseline air.

It’s a process that’s been undertaken since 1978, with about 250 canisters now held in the air archive at a CSIRO facility in Melbourne.

“By filling multiple cylinders per year over many years, we can go back and actually analyse old air when we get new instrumental techniques,” Paul Krummel, from CSIRO’s greenhouse gas and ozone-depleting substances program, said.

Climate project tries to unravel cloud mystery

While scientists have a clear picture of the past, the computations used to forecast future atmospheric changes are far less precise.

It is the reason Kennaook/Cape Grim is now hosting an important international climate project known as “CAPE-K”.

CAPE-K stands for Cloud and Precipitation Experiment at Kennaook.

It is a collaboration between the Bureau of Meteorology, the CSIRO and US Department of Energy.

“Whenever we talk about climate change and climate models, and predicting future climate, there’s always this element of uncertainty,” the Department of Energy’s Heath Powers said.

“And almost all of that uncertainty in climate models has to do with our ability — or our lack of ability — to represent clouds very, very well.”

Most climate models assume that when clouds form in freezing conditions, ice crystals develop inside them.

But for the ice to form, there usually needs to be dust or pollution in the air — something that’s not prevalent over the Southern Ocean.

The purity of the air is the reason why many of the clouds in the Southern Ocean remain in a “super-cooled liquid” state, even when the temperature falls below zero degrees Celsius.

These liquid clouds reflect more sunlight back into space than ice clouds, which means less heat is absorbed by the ocean.

But this phenomenon is not accurately incorporated into current climate calculations.

“To make these predictions much better, we need to go out and measure the types of clouds that we’re trying to represent,” Mr Powers said.

Contribution to climate modelling

Mr Powers and his team have set up dozens of sophisticated instruments at Kennaook/Cape Grim to analyse how liquid clouds are formed, and how they affect the climate.

“The thickness of clouds, the brightness of clouds, how much they rain, the size of the rain droplets that come out — these are all impacted by what [the clouds] are made out of,” he said.

“And human pollution sources versus really, really pristine clouds — like we have here — behave differently, and they impact our climate differently.”

The CAPE-K project will run until the end of 2025, providing vital new data to climate scientists around the world.

“One of the most important tools we have to be able to understand how we can mitigate and adapt to a changing climate will be these climate models,” Dr Keywood said.

“So if we get them absolutely right, then we’ve got a lot more confidence that the actions that we’re going to need to take are informed by the best available data.”

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