Figure 3.1: New Zealand national-average temperature, historical and projected
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a) New Zealand historical temperature
b) New Zealand temperature projected to 2100
Note: Shown as deviation in °C from 1961-90 climatology: (a) annual mean temperatures (black line) and a smoothed curve (red line) indicating the long-term trend; (b) reproduction of (a) but time and temperature scales expanded to encompass projected long-term trend at 2100 (range shown by vertical red bar) and extrapolated trend line (black dashed line) of 1920-2000 data.
Text description of figure
The upper panel in this figure displays the year-to-year variability of the New Zealand national-average temperature for the period from 1920 to 2000. Data are shown as departures from the 1961-1990 climatological period. Superimposed on these departures is a smoothed line to indicate the long-term trend. There is a steady increase in the New Zealand temperature series since 1920 of nearly one tenth of a degree Celsius per decade. However year-to-year changes in temperatures can be substantially larger than the 1920-2000 trend, with fluctuations up to plus or minus one degree Celsius about the long-term average.
The lower panel in this figure reproduces the upper panel, but with expanded time and temperature scales, and adds (a) an extrapolated linear trend line fitted to the 1920-2000 data, and (b) a vertical bar at 2100 spanning over three degrees Celsius represents the projected range in New Zealand temperatures scaled to the full IPCC global range. Lines joining the trend-line at 2000 to the lower and upper bounds of the 2100 projection provide an envelope of possible temperature projections.
