Hottest September on record, 2023 on track to be hottest year

5 Oct 2023

Image: © kate/

The latest data from the EU reveals that September temperatures soared past the previous record.

September 2023 was the hottest September on record, reaching average temperatures of 0.5 degrees Celsius above the previous record set in 2020 and 0.93 degrees Celsius above the average for 1991 to 2020. This is according to the latest data published today (5 October) by Copernicus, the EU’s Climate Change Service.

Compared to the pre-industrial period between 1850 and 1900, this September was 1.75 degrees Celsius hotter.

Samantha Burgess, deputy director of the Copernicus Climate Change Service, explained that the “unprecedented temperatures … have broken records by an extraordinary amount”.

“This extreme month has pushed 2023 into the dubious honour of first place – on track to be the warmest year and around 1.4 degrees Celsius above pre-industrial average temperatures,” she said.

One meteorologist, Daan van den Broek, described the data as “deeply alarming”.

“We’re not just breaking records; we’re entering uncharted territory,” he said.

Copernicus described summer 2023 as “a season of contrasting extremes”, which included calamitous heatwaves, droughts and floods around the world, with the hottest June, the hottest July and the hottest August on record.

Met Éireann has also provisionally declared July 2023 Ireland’s wettest on record. Early in the summer, Ireland and the UK also experienced a severe marine heatwave.

Record low levels of sea ice

A major result of the record-breaking temperatures has been the reduction in sea ice. Scientists have said that the Antarctic sea ice is far below previous recorded levels. The shrinking levels could have devastating consequences for rising temperatures due to its global cooling effect.

A fluffy emperor penguin chick leans into an adult penguin and another adult penguin is next to them on the ice.

An emperor penguin chick. Image: © Roger/

One noted consequence of the low sea-ice levels is the disruption to the breeding habits of emperor penguins. Researchers reported that no penguin chicks survived last year in four of their five breeding colonies. This is due to the fact that chicks hatch in late summer but don’t develop their waterproof feathers until December or January.

“Thus, the land-fast ice on which they breed must remain stable between April to January to ensure successful breeding,” the researchers wrote in their paper.

‘Humanity has opened the gates of hell’

As 2023 is set to become the warmest ever, scientists say this could be the norm in the next 10 years. Global greenhouse gas emissions have reached an all-time high this year as we rapidly burn through our remaining carbon budget (the amount of carbon dioxide we can emit into the atmosphere and stay within the 1.5 degrees Celsius warming target of the Paris Agreement).

The emergence of an El Niño climate pattern (a natural event occurring roughly every three to seven years) has precipitated a supercharged period of global warming which may lead to the passing of tipping points, past which climate recovery becomes less and less likely.

In a speech at the Climate Ambition Summit last month, UN secretary-general António Guterres described the need for climate solutions as “urgent”.

“Humanity has opened the gates of hell. Horrendous heat is having horrendous effects,” he said.

“We must make up time lost to foot-dragging, arm-twisting and the naked greed of entrenched interests raking in billions from fossil fuels.”

In December, world leaders will meet for COP28, the global climate summit.

As Burgess stated in the latest report from Copernicus: “Two months out from COP28 – the sense of urgency for ambitious climate action has never been more critical.”

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Rebecca Graham is production editor at Silicon Republic