In New Zealand the National Institute of Water and Atmospheric Research makes high-precision measurements of the three main greenhouse gases. Carbon dioxide, methane and nitrous oxide are measured at the Baring Head Atmospheric Research Station near Wellington, at Scott Base (Antarctica), and from ships and aircraft in the Pacific Ocean and Southern Ocean.
The institute has measured the background levels of atmospheric carbon dioxide since 1973, methane since 1989, and nitrous oxide since 1997. Most of the data is from clean-air samples collected at Baring Head.
The measurements record a steady rise in greenhouse gas levels over that period. For example, the release of methane into the atmosphere has increased from natural levels of about 250 million tonnes per year to about 600 million tonnes per year in the early 2000s as a result of human activities.
New Zealand’s greenhouse gas emissions
As a signatory to the United Nations Framework Convention on Climate Change, New Zealand must report annually on the quantities of greenhouse gases emitted through human activities. This inventory involves measuring emissions and determining their sources.
New Zealand is also a signatory to the Kyoto Protocol, drawn up in 1997 to implement the Convention on Climate Change. Under the protocol industrialised nations have committed to reducing their greenhouse gas emissions, between the years 2008 and 2012, to levels that are 5.2% below those of 1990.
Because many countries burn coal to generate electricity, their major greenhouse gas emissions are carbon dioxide. However, New Zealand is unique. Methane made up 37% and carbon dioxide 45% of greenhouse gas emissions in the early 2000s. This reflected the large number of farmed livestock and relatively low use of fossil fuels for generating electricity. All ruminant livestock (such as cows, sheep, deer and goats) produce methane by belching as a result of the action of anaerobic bacteria during digestion.
Nitrous oxide is also important in New Zealand’s emissions inventory, making 18% of greenhouse gas emissions in the early 2000s. It is produced through the breakdown of animal excreta and the nitrogenous fertilisers applied to farmlands.