National temperature time series

  • Image, National temperature time series.

    Emissions of greenhouse gases from human activities such as energy generation, industry, agriculture, and transportation have increased greenhouse gas concentrations in our atmosphere to levels unprecedented in the past 800,000 years. This has caused unequivocal warming in Earth’s climate system since the mid-20th century.

    Temperature is also influenced by natural processes such as climate oscillations like the El Niño Southern Oscillation (ENSO). However, ENSO does not affect the long-term trend of the national temperature time series. Temperature change can have a significant effect on agriculture, energy demand, ecosystems, and recreation.

    We classified National temperature time series as a national indicator.

    Key findings

       Increasing trend

    New Zealand’s average temperature increased at a rate of 0.95 degrees Celsius per century, meaning that our average temperature in 2016 was 1 degree Celsius warmer than in 1909. Global average land temperatures increased around 0.9–1.1 degrees Celsius a century over the same time period. These trends were assessed using linear regression at the 95 percent confidence level. 

    • From 1909, New Zealand’s warmest year was 2016. Over this period the annual average temperature was 12.3 degrees Celsius.
    • In the last 20 years we had our five warmest years: 1998, 1999, 2005, 2013, and 2016. These years had annual average temperatures above 13.1 degrees Celsius.
    Figure 1
    Note: The five-year running average is calculated as an average of the relevant year and the two years before and after. Therefore, a five-year running average was not calculated for 1909, 1910, 2015, and 2016.
    The unusual drop in temperature over 1992/3 is a result of the volcanic eruption at Mount Pinatubo, the Philippines.
    Figure 2 Graph, Annual average temperature anomaly (difference from normal), 1909–2016.
    Note: The annual average temperature anomaly (difference from normal) is calculated based on the climate normal period from 1981 to 2010.
    The five-year running average is calculated as an average of the relevant year and the two years before and after. Therefore, the five-year running average was not calculated for 1909, 1910, 2015, and 2016.
    Figure 3
    Note: Annual average temperature anomalies (difference from normal) are calculated based on the climate normal period from 1981 to 2010.
    The five-year running average is calculated as an average of the relevant year and the two years before and after. Therefore, the five-year running average was not calculated for 1909, 1910, 2015 and 2016.
    CRU – Climatic Research Unit; NASA – National Aeronautics and Space Administration; NOAA – National Oceanic and Atmospheric Administration

    Definition and methodology

    New Zealand temperature

    NIWA's 'seven-station' temperature series uses temperature measurements from seven 'climate stations' (NIWA, nd-a). The sites offer a representative geographical spread with reliable records dating back to the early 1900s.

    We analysed the linear trend in New Zealand’s temperature from 1909 to 2016 because climate change is best understood over a long term, using consistent methodology – considerable year-to-year variability makes it difficult to discern trends over the short term.

    For each site, NIWA merged temperature records from local sites to form a long time series. The data are adjusted for climatic differences between sites and changes in exposure or instrumentation at the same site. This prevents the introduction of significant biases with time.

    Reasons for climatic differences between sites include:

    •  altitude – a higher site is generally colder than a lower site (eg in Wellington, the measuring site at Kelburn is about 120 metres higher than the one at Thorndon)
    • exposure to the elements – a wind-swept site is generally colder than a protected site.

    This methodology has been reviewed nationally and internationally (NIWA, nd-b).

    Global land temperature

    Global mean annual ‘land surface only’ temperature anomaly data was sourced from:

    Global mean annual temperature anomalies (difference from normal) are based on the same period used for the New Zealand data (1981–2010). For further information on the global datasets and why they differ, see Hartmann et al (2013).

    Increasing temperatures

    Human activities have increased greenhouse gas concentrations in our atmosphere to levels unprecedented in the past 800,000 years and the IPCC has concluded that “the science now shows with 95 percent certainty that human activity is the dominant cause of observed warming since the mid-20th century” (Intergovernmental Panel on Climate Change (IPCC), 2013). For more information see Greenhouse gas concentrations.

    Data quality

    We classified National temperature time series as a national indicator.

    Relevance

       This national indicator is a direct measure of the ‘Climate' topic. 

    Accuracy

       The accuracy of the data source is of high quality.

    See Data quality information for more detail.

    References

    Hartmann, D, Klein Tank, A, Rusticucci, M, Alexander, L, Brönnimann, S, Charabi, Y, & Zhai, P (2013). Observations: Atmosphere and surface. In Stocker, TF, Qin, D, Plattner, GK, Tignor, M, Allen, SK, Boschung, J,… Midgley, PM (Eds), Climate change 2013: The physical science basis. Working Group I Contribution to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge and New York: Cambridge University Press.

    Intergovernmental Panel on Climate Change (IPCC) (2013). Climate change 2013: The physical science basis. Working Group I Contribution to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. [Stocker, TF, Qin, D, Plattner, GK, Tignor, M, Allen, SK, Boschung, J,… Midgley, PM (Eds)], Cambridge and New York: Cambridge University Press.

     NIWA (nd-a). NZ temperature record. Retrieved 15 May 2017 from www.niwa.co.nz.

     NIWA (nd-b). NZ temperature record – review. Retrieved 15 May 2017 from www.niwa.co.nz.

    Archived pages

    See National temperature time series (archived October 2017).

     

    Updated 19 October 2017

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