New York, New York - The Earth is suffering a "climate breakdown," the head of the UN said on Wednesday, after data showed the last three months have been the hottest since records began in 1940.

UN Secretary General António issued a stark statement as another grim milestone was passed.

"Global temperature records continue to tumble in 2023, with the warmest August following on from the warmest July and June," said Samantha Burgess, the deputy director of the EU's Copernicus Climate Change Service.

The average temperature during the June to August period was 16.77 degrees Celsius (62.18 degrees Fahrenheit), 0.66 degrees above average and once again significantly higher than the previous record of 16.48 degrees set in 2019.

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The eight-month January to August period was the second-warmest on record after 2016, when there was a strong warming El Niño event, the agency said.

The climate phenomenon that sees water temperatures rise in the Pacific is building up again – causing climate experts to look ahead with concern.

In a separate statement, the UN's World Meteorological Organization (WMO) described August as the hottest month on record "by a large margin" and the second-hottest ever month after July 2023.

August also saw the highest global monthly average sea surface temperatures on record at 20.98 degrees Celsius (69.76 degrees Fahrenheit).

"Our planet has just endured a season of simmering – the hottest summer on record. Climate breakdown has begun," Guterres said.

"Scientists have long warned what our fossil fuel addiction will unleash. Surging temperatures demand a surge in action. Leaders must turn up the heat now for climate solutions. We can still avoid the worst of climate chaos – and we don’t have a moment to lose," he said.

WMO Secretary General Petteri Taalas said the Northern Hemisphere had endured "a summer of extremes," pointing in particular to the devastating wildfires that have scorched wide swathes of land and harmed the health of populations.

"In the Southern Hemisphere Antarctic sea ice extent was literally off the charts, and the global sea surface temperature was once again at a new record," he said.

He noted that these higher temperatures are happening "before we see the full warming impact of the El Niño event," which is expected to push temperatures higher in the second year after it develops.