Measuring the air that we breathe

Atmospheric chemist Dave Lowe at his Plimmerton home, Porirua. Photo / Mark Mitchell

When Dave Lowe rigged an air tube up a wind-battered lighthouse flagpole in 1972, people were still talking about another ice age.

Sure, his American boss had just made the ground-breaking discovery that carbon dioxide levels in the atmosphere were rising, but nobody knew what that meant.

Lowe laughs now when he remembers it. "I must have been one of the only people in the world who had heard of global warming."

Thirty years later, his measurements are part of probably the biggest summary of scientific reports in history. It is now the oldest record we have of what has happened to Southern Hemisphere CO2.

Lowe had just graduated with a physics degree when he was recommended to work on the project by nuclear chemist Athol Rafter.

United States scientist Dave Keeling - inventor of the upward-climbing chart of atmospheric CO2 known as the Keeling Curve - wanted somebody to start measuring in the Southern Hemisphere to see if CO2 growth matched what he was seeing in the north.

After one false start, Lowe found the windiest, most barren headland he could - Baring Head near the entrance to Wellington Harbour - and built an automatic air-sampling machine using parts from a telephone exchange.

He had to make sure there was nothing to change the air between him and Antarctica - no plants, no cars, no fires. During a southerly at Baring Head, the Antarctic winds came straight over the ocean.

What Lowe and Keeling found was remarkable. Not only was the planet breathing - in during the Northern Hemisphere growing season as plants sucked up more CO2, out during the northern winter, when the deciduous trees dropped their leaves - but the amount of CO2 left in the atmosphere after each breath was rising.

At Baring Head, where the southerlies were largely free of the effect of Northern Hemisphere plant life, the trend was starker than in the north. "We were measuring the same trend as Dave Keeling measured in the Northern hemisphere but ... the seasonal cycle wasn't there," said Lowe.

Scientists would later "fingerprint" the carbon to prove it was coming from people burning fossil fuels, and the Baring Head measuring station would expand to chart rising methane and other greenhouse gases. Ultimately it would be used when the Intergovernmental Panel on Climate Change concluded in 2007 that it was very likely - 90 per cent certain - that rising greenhouse gases were to blame for most warming in global average temperatures since the mid 20th century.

During the time it took to gather evidence of rising greenhouse gases, other scientists were charting its effects. Flights over 50 South Island glaciers every March since 1977 charted the loss of about half the glaciers' ice since the 1900s in response to about 1C of warming, said Niwa snow and ice scientist Jordy Hendrikx.

Hendrikx said that although the glaciers grew for a while in the 1980s and 1990s, thanks to a spike in westerlies, the overall trend was melting. He said there would be significant losses if temperatures warmed beyond 2C - the point many countries have set as their maximum.

To achieve that the panel has told world governments that CO2 concentration must not pass 450 parts per million. Already the Baring Head records show CO2 rising from about 325 ppm in 1972 to about 380 ppm. .

Even when global warming was unheard of, Lowe said the significance of that was obvious. After eight years, the project was considered important enough to be handed over to another respected climate scientist, Martin Manning, when Lowe won a scholarship to study in Germany.

"It was clear by then that the project was incredibly important," said Lowe. The work is now done by Niwa which has more than 20 scientists working in the field.

"Martin and I could see that this was a huge area of science that was going to take off."