Climate Change Chart of Cardiff, Great Britain

Overview of climate changes

Temperature changes

Averaged across calendar months, monthly mean temperature shows a difference of +0.64 °C compared with the earlier reference period. This unweighted comparison summarizes the monthly means; it is not a day-weighted annual average or a measure of daytime maximum temperatures, and it does not establish a continuous change between the periods. The largest monthly mean temperature increase was in December, at a difference of +1.47 °C. By contrast, April had the largest decrease, a difference of -0.22 °C; these are the most pronounced monthly changes in their respective directions, not a description of every month.

Changes in rainfall

Averaged across calendar months, mean daily rainfall had a difference of +0.96 mm/day compared with the earlier reference period. This is an unweighted summary of monthly means, not a day-weighted annual average, and the measure describes daily amounts rather than monthly rainfall totals. The largest monthly increase in mean daily rainfall occurred in December, with a difference of +2.26 mm/day. This identifies the strongest increase among the monthly means; it does not imply that rainfall increased in every month or on every day.

Changes in sunshine duration

Averaged across calendar months, mean daily sunshine duration had a difference of -0.23 hours/day compared with the earlier period. The unweighted monthly-mean comparison is a summary across calendar months, not a day-weighted annual figure or evidence of a continuous trend. The largest decrease in mean daily sunshine was in December, at a difference of -0.87 hours/day. In July, the largest monthly increase was a difference of +0.24 hours/day; these contrasting extrema do not describe the pattern in every month.

Changes in snowfall

Averaged across calendar months, mean daily snowfall had a difference of -0.16 mm/day compared with the earlier reference period. This is an unweighted summary of monthly means, not a day-weighted annual average, and it should not be read as evidence that snowfall was absent. The largest monthly decrease in mean daily snowfall occurred in January, with a difference of -1.84 mm/day. The largest increase was in March, at a difference of +0.48 mm/day; these monthly changes show contrasting directions rather than a uniform shift across all months.