Climate Change Chart of Georgetown, Saint Helena, Ascension and Tristan da Cunha

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 summary describes monthly means, not daytime maximum temperatures or a change shared by every month. The largest monthly increase was in December, with a difference of +0.78 °C. This identifies the strongest reported increase among the monthly means, rather than implying that every month changed by the same amount.

Changes in rainfall

Averaged across calendar months, mean daily rainfall shows a difference of -0.11 mm/day compared with the earlier reference period. This unweighted summary of monthly means is not a day-weighted annual average, and it does not indicate that rainfall decreased in every month. The monthly pattern includes contrasting extremes: March had the largest increase, a difference of +0.24 mm/day, while July had the largest decrease, a difference of -0.39 mm/day. These are differences in mean daily amounts, not monthly rainfall totals, and describe the selected months rather than daily variability.

Changes in sunshine duration

Mean daily sunshine duration shows an unweighted difference of -0.28 hours/day averaged across calendar months. This aggregate comparison of monthly means does not mean that sunshine declined by the same amount in every month. The largest monthly decrease in mean daily sunshine was in September, with a difference of -0.77 hours/day. That monthly contrast marks the largest reported decrease, not a description of every day's sunshine or a continuous change between the reference periods.