Climate Change Chart of Atlanta, USA

Overview of climate changes

Temperature changes

Averaged across calendar months, monthly mean temperature shows a difference of +0.58 °C compared with the earlier reference period; this is an unweighted mean of monthly averages, not a day-weighted annual figure or a measure of daytime highs. The monthly shifts were not uniform: December had the largest increase, a difference of +1.83 °C, while June had the largest decrease, a difference of -0.34 °C. These extrema describe changes in monthly means, not conditions on every day in those months.

Changes in rainfall

Mean daily rainfall, rather than monthly rainfall totals, averaged across calendar months shows a difference of +0.94 mm/day in the more recent period. That unweighted mean summarizes the monthly averages, while individual months differed: August recorded the largest increase, a difference of +1.58 mm/day, and March the largest decrease, a difference of -0.10 mm/day. These comparisons concern average daily amounts within each month and do not describe every day’s rainfall.

Changes in sunshine duration

Mean daily sunshine duration had an unweighted difference averaged across calendar months of -0.03 hours/day. The overall monthly-average comparison is close to unchanged, but it does not mean sunshine was identical month by month: July had the largest increase, a difference of +0.54 hours/day, whereas February had the largest decrease, a difference of -0.62 hours/day. These are differences in mean daily hours, not measures of every day’s sunshine.

Changes in snowfall

Mean daily snowfall, not monthly snowfall totals, had an unweighted difference across calendar-month averages of -0.02 mm/day. The modest aggregate difference sits alongside contrasting monthly changes: February had the largest increase, a difference of +0.63 mm/day, while January had the largest decrease, a difference of -0.78 mm/day. These are changes in average daily snowfall by month; the overall mean does not imply that every month changed in the same direction or that snowfall was absent when averages were small.