In brief: Answers in the wind at Baring Head
What can 40 years’ worth of CO2 measurements tell us? An awful lot, says Dr Mike Harvey. “We want to know how the concentration of CO2 in the atmosphere changes over time, in relation to what we’re emitting into the atmosphere.”
A little over half of CO2 emissions are taken up by the land and ocean, says Harvey, NIWA’s Baring Head Clean Air Observation Programme Leader. The rest persists in the atmosphere, “So by measuring that precisely, we have a better understanding of how much energy is trapped in the atmosphere as a result of greenhouse gases.”
The Baring Head facility was conceived in 1969 by the then Department of Scientific and Industrial Research, and began measuring CO2 on 14 December 1972. One of only a handful of monitoring stations in the Southern Hemisphere, it sits atop a sea cliff on the eastern side of the Wellington Harbour entrance. Its 40 years of data comprise the second-longest continuous measurement record in the world (the longest comes from a station atop Mauna Loa in Hawaii, begun in 1958), and the longest in the Southern Hemisphere. Research has since expanded into other greenhouse and trace gases.
The windy site is perfect, says Harvey. Baring Head stands squarely in the path of a ‘clean’ sample of mid-latitude southerlies, typically unsullied by contact with any land for the last five days.
So what are those southerlies showing us? “The 40-year trend,” says Harvey, “shows atmospheric CO2 increasing each year, currently at a rate of around two parts per million (ppm) or 0.5 per cent, every year. CO2 concentrations recorded at Baring Head now – at 390 ppm – are 20 per cent greater than when measurements began, at 325 ppm.
The effects from any global efforts to cut CO2 emissions should start showing up in the record in coming decades, he says. Nevertheless: “As the century progresses, we could move to quite a different climate to what we have today. If CO2 emissions continue unabated, major global economic impacts are expected from the increasing severity of climate change extremes.” New Zealand, he says, is at the forefront of new measuring technologies. “We use lasers to make raw measurements of CO2 and methane once every few seconds. Our research adds measurements from Baring Head to a meteorological modelling framework, to estimate the regional distribution of sources and sinks of CO2.” The station also sends its data to an intercalibrated network called the Global Atmosphere Watch, coordinated by the World Meteorological Organization.
NIWA also makes atmospheric measurements at its Lauder station in Central Otago, Rainbow Mountain near Rotorua and Arrival Heights in Antarctica.