Climate Change Chart of Dunedin, New Zealand

Overview of climate changes

Temperature changes

Averaged across calendar months, monthly mean temperature shows a difference of +1.55 °C compared with the earlier reference period. This is an unweighted mean of monthly means, not a day-weighted annual average, and it does not mean every month warmed by the same amount. The largest monthly increase was in June, with a difference of +2.52 °C. This month-specific comparison complements the overall mean and describes monthly mean temperature, not daytime maximum temperatures.

Changes in rainfall

Averaged across calendar months, mean daily rainfall had a difference of +0.27 mm/day. This unweighted mean of monthly means is not a day-weighted annual average, and it should not be read as an increase in every month's rainfall. The largest monthly increase in mean daily rainfall occurred in June, with a difference of +1.06 mm/day; the largest monthly decrease was in December, with a difference of -0.66 mm/day. These are daily means, not monthly rainfall totals, and the contrasting changes show that the overall mean does not describe each month.

Changes in sunshine duration

Averaged across calendar months, mean daily sunshine duration had a difference of -0.40 hours/day compared with the earlier period. This is an unweighted mean of monthly means, so it summarizes the calendar months rather than indicating the same change in sunshine for each month. The largest monthly decrease was in September, with a difference of -0.70 hours/day. This month-specific result describes mean daily sunshine duration and should not be generalized to every month.

Changes in snowfall

Averaged across calendar months, mean daily snowfall had a difference of +0.09 mm/day. This unweighted mean summarizes monthly means rather than day-weighted annual snowfall, and it does not imply an equal increase in every month. The largest monthly increase in mean daily snowfall was in July, with a difference of +0.28 mm/day; the largest monthly decrease was in June, with a difference of -0.03 mm/day. These are daily mean amounts, not monthly totals, and the month-specific differences need not match the overall average change.