Greenhouse gas concentrations

  • Image, Greenhouse gas concentrations.

    Greenhouse gases (GHGs) act like a blanket around Earth, trapping warmth from the sun and making life on our planet possible. Emissions from human activities, such as energy generation, industry, agriculture, and transportation, have increased the amount of GHGs in our atmosphere. GHG concentrations are now far higher than at any other time in the past 800,000 years. This has caused Earth to heat at an unprecedented rate, sea levels to rise, glaciers to melt, and oceans to acidify.

    We report on GHG concentrations in ‘clean air’ measured at Baring Head, near Wellington. These measurements give us a good idea of global concentrations and help us infer long-term impacts on ocean acidity, temperature, sea level, and glaciers.

    We assessed Greenhouse gas concentrations as a national indicator.

    Key findings

     Image, Increasing trend, declining state.  Increasing trend (declining state)

    Carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) concentrations at Baring Head, Wellington increased since their measurements started.

    At the 95 percent confidence level:

    • CO2 increased 23 percent from 326 parts per million (ppm) in December 1972 to 401ppm in December 2016 (a rate of increase of 1.6ppm a year), surpassing the symbolic threshold of 400ppm. This increase is associated with burning fossil fuels, cement production, and land use change.
    • CH4 increased 9 percent from 1,659 parts per billion (ppb) in August 1989 to 1,810ppb in September 2016 (a rate of increase of 4.3ppb a year). This increase is associated mostly with agriculture and fossil fuel production.
    • N2O increased 6 percent from 312ppb in August 1996 to 330ppb in December 2016 (a rate of increase of 0.87ppb a year). This increase is primarily linked to increased use of nitrogen-based fertilisers in cropping, soil cultivation, and depositing animal waste on pasture.
    Figure 1
    Note: Data are unavailable for some periods.
    Figure 2
    Note: Data are unavailable for some periods.
    Figure 3
    Note: Data are unavailable for some periods.

    Definition and methodology

    We report on three greenhouse gases: carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Water vapour is also an important greenhouse gas but we do not report on it because increased concentrations are a response to warming as well as a cause of it (through positive feedback). However, water vapour stays in the atmosphere a very short time and concentrations cannot be controlled by humans.

    Greenhouse gases are generally well mixed around the globe. ‘Clean air’ observations from Baring Head, near Wellington, are made when the air’s trajectory is from the south and away from any likely local sources of gas emissions. These observations give a representative estimate of concentrations over the Southern Ocean and are an internationally representative measure of global concentrations (NIWA, nd; IPCC, 2007). Note however, that greenhouse gas concentrations are slightly lower in the Southern Hemisphere compared with the Northern Hemisphere, because the Northern Hemisphere is the larger source of greenhouse gases and air takes time to exchange across the tropical belt.

    Emissions from human activities, such as energy generation, industry, agriculture, and transportation, have increased the amount of GHGs in our atmosphere. GHG concentrations are now far higher than at any other time in the past 800,000 years (IPCC, 2014).

    The Intergovernmental Panel on Climate Change (IPCC) concluded that “Warming in the climate system is unequivocal, and …. It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century” (IPCC, 2013). New Zealand’s temperature has been increasing in line with global temperature increases. Our temperature rose 1 degree Celsius from 1909 to 2016, and our five warmest years occurred in the last 20 years. See National temperature time series for more information on our temperature increases.

    Data quality

    We assessed Greenhouse gas concentrations as a national indicator.

    Relevance

       This national indicator is a direct measure of the ‘Atmospheric properties’ topic.

    Accuracy

    Image, High accuracy.    The accuracy of the data source is of high quality.

    See Data quality information for more detail.

    References

    Intergovernmental Panel on Climate Change (IPCC) (2007). In Solomon, S, Qin, D, Manning, M, Chen, Z, Marquis, M, Averyt, KB, … Miller, HL (Eds), Climate change 2007: The physical science basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Retrieved from www.ipcc.ch.

    Intergovernmental Panel on Climate Change (IPCC) (2013). In Stocker, TF, Qin, D, Plattner, GK, Tignor, M, Allen, SK, Boschung, … Midgley, PM (Eds), Climate change 2013: The physical science basis (PDF 755kB). Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Retrieved from www.ipcc.ch.

    Intergovernmental Panel on Climate Change (IPCC) (2014). Climate change 2014: Synthesis report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (PDF, 11MB). Retrieved from www.ipcc.ch.

    NIWA (nd). Baring Head greenhouse gases. Retrieved 29 June 2017 from www.niwa.co.nz

    Archived pages

    See Greenhouse gas concentrations (archived October 2017).

    Updated 19 October 2017

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