Climate Change Chart of Sommaroy, Norway

Overview of climate changes

Temperature changes

Averaged across calendar months, monthly mean temperature shows a difference of +0.74 °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 imply the same difference in every month or describe daytime maximum temperatures. The largest monthly increase was in July, with a difference of +1.70 °C; the largest monthly decrease was in December, with a difference of -0.49 °C. These opposing monthly changes show why the overall mean should not be read as a uniform change throughout the year.

Changes in rainfall

For mean daily rainfall, averaged across calendar months, the difference was +0.04 mm/day compared with the earlier reference period. This is an unweighted average of monthly means, not a day-weighted annual figure, and it describes daily mean amounts rather than monthly rainfall totals. The largest monthly increase occurred in July, with a difference of +1.29 mm/day, while the largest monthly decrease occurred in October, with a difference of -1.26 mm/day. The overall mean difference does not mean rainfall changed by the same amount in every month.

Changes in sunshine duration

Mean daily sunshine duration, averaged across calendar months, had a difference of -0.23 hours/day in the more recent period. This unweighted mean of monthly means summarizes the calendar months rather than a day-weighted annual average, and does not indicate that every month changed in the same way. The largest monthly decrease was in June, with a difference of -0.93 hours/day; the largest monthly increase was in August, with a difference of +0.24 hours/day. These are changes in mean daily hours for the named months, not a measure of sunshine on every individual day.

Changes in snowfall

Mean daily snowfall, averaged across calendar months, shows a difference of +1.29 mm/day compared with the earlier reference period. This is an unweighted average of monthly means, not a day-weighted annual amount or a monthly total. The largest monthly increase was in March, with a difference of +8.30 mm/day, while the largest monthly decrease was in October, with a difference of -3.57 mm/day. The monthly contrasts mean the aggregate difference should not be taken to describe every month's daily snowfall.