You are here: Environmental reporting 
Atmosphere Greenhouse gases
Levels of atmospheric greenhouse gases
Levels of three greenhouse gases in the atmosphere over New Zealand are measured at Baring Head, to the southeast of Wellington. These greenhouse gases are:
- carbon dioxide
- methane
- nitrous oxide.
The measurements at Baring Head are representative of atmospheric gases over a wide region of the ocean to the south of New Zealand.
Long-term trends
The level of all three gases has increased in the past 35 years. The trends in greenhouse gas concentrations observed at Baring Head are consistent with global trends in atmospheric greenhouse gas concentrations. It is the global atmospheric concentration of greenhouse gases that determines the risk of climate change.
Carbon dioxide
Levels at Baring Head have risen from 324 parts per million (ppm) in 1970, to 379 ppm in 2006. The 35-year record measured at Baring Head has an average growth rate of 1.5 ppm each year. The average growth rate of carbon dioxide concentration in the past 10 years of 1.9 ppm is greater than at any other time over the instrumental record starting in 1960. This trend is supported by global observations.
Atmospheric levels of carbon dioxide (CO2) at Baring Head, 1970 - 2006
Source: National Institute of Water and Atmospheric Research.
Methane
Levels at Baring Head show an annual growth rate from 1989 to 1997 of 6.5 parts per billion (ppb) each year. Since 1998, there has been a small decrease in methane concentrations in recent years. This pattern is reflected in measurements taken at Arrival Heights, Antarctica and other global sites. It is not fully understood what drives these changes in methane concentrations.
Atmospheric levels of methane (CH4) at Baring Head, 1989 - 2007
Source: National Institute of Water and Atmospheric Research.
Nitrous oxide
Levels at Baring Head indicate a steady growth trend. Seasonal variation is very small compared with the annual growth rate, because of the long atmospheric lifetime of nitrous oxide. The average annual growth rate is 0.9 ppb each year.
Atmospheric levels of nitrous oxide (N2O) at Baring Head, 1997 - 2007
Source: National Institute of Water and Atmospheric Research.
What can you do?
Many day-to-day activities contribute to greenhouse gas emissions.
You can reduce greenhouse gases by reducing the amount of electricity you use at home, by changing your transport habits and by reducing your waste.
For example:
- Lose the heavy stuff – each 50 kg of extra weight in your car increases fuel consumption by around 2 per cent. Remove your roof rack when you don't need it and save even more fuel.
- Switch off appliances at the wall – the average household could save around 10 per cent on its power bill if appliances on standby were switched off.
Text description for three graphs above: line graphs showing the atmospheric levels of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) at Baring Head, Wellington.
The level of carbon dioxide in the atmosphere measured at Baring Head has risen from 324 ppm in 1970 to 379 ppm in 2006. This is a steady trend with an average growth rate of 1.5 ppm per year.
The level of methane rose steadily from 1989 to 1997 by 6.5 ppb each year. There is strong seasonal variation in methane concentration. Since 1998 concentrations of methane have levelled off, with a small decrease in recent years.
The level of nitrous oxide shows steady growth from less than 312 ppb in 1997 to almost 322 ppb in 2007. The average annual growth rate is 0.9 ppb each year.
This information has come from the latest national state of the environment report Environment New Zealand 2007.
Move to the next page on greenhouse gas emissions and removals
Last updated: December 2007
