Climate Change Chart of Chamonix Mont-Blanc, France

Overview of climate changes

Temperature changes

Averaged across calendar months, monthly mean temperature shows a difference of +2.41 °C compared with the earlier reference period; this is an unweighted mean of the monthly means, not a day-weighted annual average or a measure of daytime maximum temperatures. The strongest month-specific increase was in December, with a difference of +5.03 °C. This identifies the largest monthly increase, rather than describing every month's change.

Changes in snowfall

Mean daily snowfall averaged across calendar months shows a difference of +6.68 mm/day in the more recent period. This is an unweighted mean of monthly means, not a day-weighted annual average, and the amounts are daily means rather than monthly totals. The largest monthly increase was in March, where the difference was +18.11 mm/day. This peak month adds detail to the overall average but does not imply that snowfall increased by the same amount in other months.

Changes in rainfall

Mean daily rainfall averaged across calendar months shows a difference of +0.73 mm/day in the more recent period. This unweighted mean of monthly means is not a day-weighted annual average, and the figures describe daily amounts rather than monthly totals. The largest monthly increase was in May, at a difference of +1.82 mm/day. By contrast, November had the largest monthly decrease, with a difference of -0.29 mm/day; these extrema show that the average increase did not apply uniformly across months.

Changes in sunshine duration

Mean daily sunshine duration, averaged across calendar months, had a difference of -0.26 hours/day compared with the earlier reference period. This is an unweighted mean across monthly means, not a day-weighted annual measure. The largest monthly decrease occurred in May, with a difference of -0.72 hours/day; that month-specific result should not be taken to represent every month.