Scientists say it's a clear indication of temperatures being driven up by emissions from human society.
The.05°C increase in surface air temperatures last month makes it the hottest September on record globally, according to experts from the EU's Copernicus Climate Change Service (C3S).
But even though large emitters, including China and European Union nations, have pledged to slash their emissions in the coming decades, overall, current policies would see temperatures rise far beyond the 1.5 degree level.
That is alarmingly close to the 1.5C threshold for severe impacts detailed in a major 2018 report by the UN's climate science advisory panel, the IPCC. Also, the Paris Agreement has urged nations to cap global warming at "well below" 2C, and 1.5C if possible.
The warmest calendar year on record for Europe was 2019, though by only a narrow margin. "Some months it's warming more, and some months less, some years more, and some less". This year is also projected to break a temperature record, despite an initial drop in emissions due to the pandemic.
Across California five of the state’s six biggest wildfires in history were still burning at the end of September
Monitors of the Paris Climate Agreement will view the figures with particular alarm: for the 12-month period through to September 2020, the planet was almost 1.3 degrees Celsius (2.4 degrees Fahrenheit) warmer than pre-industrial levels.
In fact, it was this global rise in temperatures which caused devastating wildfires in Australia, the USA and caused weird weather across the globe. And it helped fuel the torrential downpours that flooded the south of France with more than half a meter of rain in a day. Much of the continent saw above-average temperatures, especially southeastern Europe.
C3S has also confirmed that the average Arctic sea ice extent for September was the second-lowest recorded, after 2012.
Additionally, Arctic sea ice has also reached its second-lowest point since the inception of satellite records.
Last month's global record for heat was all the more remarkable because of the regional cooling effect of a naturally occurring La Nina weather event over the tropical Pacific.
The latest average, to September 2020, is about 1.6° above the 1981-2010 average.