Dave Lowe on measuring CO2 in New Zealand for 50 years, and how Carbon Watch NZ is a bird's eye view on our carbon balance.

Carbon Watch NZ is a collaborative project to measure our greenhouse gases - where they are coming from and where they are going to.

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When it comes to greenhouse gases in the atmosphere, the biggest culprit is carbon dioxide (CO2) - and it's something that New Zealand has been interested in for a long time.

New Zealand is home to the longest running continuous carbon dioxide measurements in the southern hemisphere, second only to Hawaii in the northern hemisphere.

Measurements began here fifty years ago, initially at Makara, near Wellington. They were set up by atmospheric scientist Dave Lowe, who worked for many years at NIWA.

Since 1972, measurements have been made at the Baring Head clean air station on the north side of Cook Strait near Wellington.

Atmospheric carbon dioxide levels before the Industrial Revolution were 280 parts per million (PPM).

Dave vividly remembers the first measurements he recorded at Baring Head.

"It was in December 1972, and yes, it was very exciting," says Dave. "We used chart recorders back then and you saw this straight line, which meant that you were measuring an incredibly stable CO2 concentration - and it was around 323 parts per million."

Carbon dioxide concentrations in the atmosphere have since risen to around 410 PPM.

"In my working lifetime it's gone up around 90 parts per million," says Dave. "And that's the whole of the earth's atmosphere. It's a huge hit on the chemical and physical properties of the earth's atmosphere - the only atmosphere that we have."

Keeling's contribution

NIWA technician Gordon Brailsford is an expert in measuring atmospheric gases, and he says that when he began work in this area, CO2 levels were at 347 PPM.

Although sophisticated technology is now used for measuring many types of atmospheric gases, Gordon says that they also still use a method that Dave began using back in the early 1970s.

Keeling bottles were developed by American scientist Charles 'Dave' Keeling, who began the first long term CO2 measurements in Hawaii in 1958.

They are a vacuum flask, which are filled with air by opening the valve "into the teeth of a southerly wind" and sucking in air that, at Baring Head, has blown across the southern ocean from Antarctica.

This clean oceanic air provides background measurements of CO2 concentration that are not influenced by processes on land…

Go to this episode on rnz.co.nz for more details