In response to the assessment by the Copernicus Climate Change Service, the UN warned that until humanity weaned off fossil fuels, the planet would only push deeper into uncharted territory.
Copernicus observations go back to 1940 but other evidence - such as ice cores, tree rings and coral skeletons - allow scientists to place today's climate against a much longer historical context.
"Humans haven't seen temperatures as hot as today for, arguably, at least the last 100,000 years," Samantha Burgess from the European Center for Medium-Range Weather Forecasts, which oversees Copernicus, told AFP.
Global average air temperatures in August were 16.96 C, Copernicus said - surpassing by 0.01 C the previous all-time monthly record set in July 2023. Copernicus said it considered the two months joint-highest given the narrow difference.
Scientists say that human activity - primarily the burning of coal, oil and gas - has warmed the planet by roughly 1.4 C since pre-industrial times and increased the severity and likelihood of extreme weather.
