Climate Change Chart of Brussels, Belgium

Overview of climate changes

Temperature changes

Averaged across calendar months, monthly mean temperature shows a difference of +1.32 °C in the more recent period; this is an unweighted comparison of monthly means, not a day-weighted annual average or a measure of daytime maximum temperatures. The largest monthly increase was in January, with a difference of +3.03 °C. By contrast, April had the largest decrease, a difference of -0.32 °C. These extremes show that the overall mean difference does not describe every month’s change.

Changes in rainfall

Mean daily rainfall, rather than monthly totals, averaged a difference of +0.39 mm/day across calendar months between the periods. This unweighted mean summarizes the monthly comparisons and does not imply the same change in every month. The largest increase occurred in December, with a difference of +0.85 mm/day; the largest decrease was in April, at a difference of -0.61 mm/day. The opposing monthly changes provide useful context for the overall mean, without indicating a uniform pattern through the year.

Changes in snowfall

Mean daily snowfall, not monthly snowfall totals, averaged a difference of -0.09 mm/day across calendar months. This unweighted comparison captures the mean of the monthly values and does not mean that snowfall was absent or changed equally in every month. The largest decrease was in February, with a difference of -0.75 mm/day; the largest increase occurred in April, at a difference of +0.24 mm/day. The contrast between these monthly extremes shows why the average difference should not be read as a month-by-month description.

Changes in sunshine duration

Mean daily sunshine duration averaged across calendar months had a difference of -0.26 hours/day in the more recent period. This is an unweighted mean of monthly means, so it summarizes the calendar months rather than describing every day or month. The largest monthly decrease was in January, with a difference of -0.96 hours/day, while the largest increase occurred in February, at a difference of +0.31 hours/day. These monthly extremes help explain why a single mean difference cannot represent sunshine changes in each part of the year.