Climate Change Chart of London, Great Britain

Overview of climate changes

Temperature changes

Averaged across calendar months, monthly mean temperature shows a difference of +0.95 °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 highs. The largest monthly increase was in December, at a difference of +1.93 °C. By contrast, April had the largest monthly decrease, a difference of -0.38 °C. These month-specific differences show that the overall mean does not describe every month equally.

Changes in snowfall

Mean daily snowfall had an unweighted difference across calendar months of -0.14 mm/day. The largest monthly decrease was in January, with a difference of -0.98 mm/day, while November had the largest increase, at a difference of +0.03 mm/day. These are differences in daily means, not monthly snowfall totals, and the across-month mean does not describe each month's change; recorded snowfall in at least one reference period is reflected in the supplied snowfall differences.

Changes in sunshine duration

Mean daily sunshine duration had an unweighted difference across calendar months of -0.26 hours/day. Monthly differences were not uniform: February recorded the largest increase, a difference of +0.46 hours/day, while June recorded the largest decrease, a difference of -1.10 hours/day. The aggregate mean therefore summarizes the set of monthly averages; it does not imply the same change in daily sunshine for each month.

Changes in rainfall

Mean daily rainfall, rather than monthly rainfall totals, had an unweighted across-month mean difference of +0.57 mm/day compared with the earlier reference period. The largest monthly increase was recorded in October, with a difference of +1.13 mm/day; in April, the largest monthly decrease was a difference of -0.11 mm/day. These particular months help show why the mean across calendar months should not be read as a uniform change in daily rainfall throughout the year.