Climate Change Chart of Banff National Park, Canada

Overview of climate changes

Temperature changes

Averaged across calendar months, the difference in monthly mean temperature was +1.00 °C. This is an unweighted comparison of monthly means, not a day-weighted annual average, and it does not describe daytime maximum temperatures or imply that every month changed by the same amount. The largest monthly increase was in January, with a difference of +3.36 °C; by contrast, December had the largest decrease, at -0.79 °C. These opposing monthly differences show why the overall mean should not be read as a uniform change throughout the year.

Changes in snowfall

Mean daily snowfall, averaged across calendar months, had a difference of +0.31 mm/day in the more recent period. This unweighted average describes monthly mean daily amounts, not monthly snowfall totals, and it does not establish that snowfall increased in every month. The largest monthly increase occurred in December, with a difference of +3.60 mm/day, while the largest decrease was in May, at -3.20 mm/day. The contrasting monthly differences help explain why the overall mean is only a summary across calendar months.

Changes in rainfall

Mean daily rainfall, averaged across calendar months, had a difference of -0.26 mm/day in the more recent period. This unweighted mean of monthly figures is not a day-weighted annual average, and the daily amounts should not be mistaken for monthly totals. The largest monthly decrease occurred in July, with a difference of -1.11 mm/day, while November recorded the largest increase, at +0.07 mm/day. The mean therefore summarizes a set of monthly differences rather than indicating the direction of change in every month.

Changes in sunshine duration

Averaged across calendar months, mean daily sunshine duration had a difference of -0.24 hours/day compared with the earlier reference period. This is an unweighted mean of monthly daily-hour figures, not a day-weighted annual measure, and it does not mean that sunshine duration decreased in every month. The largest monthly decrease was in December, at -0.70 hours/day; June had the largest increase, with a difference of +0.47 hours/day. These monthly contrasts provide context for the overall mean without suggesting a continuous trend between the reference periods.