September 2023 was not only the hottest September on record, new data has confirmed today, but it was warmer by a margin described by stunned scientists as “extraordinary”, “huge” and “whopping”.
It keeps the world on course for its hottest year ever, expected to be 1.4C warmer than before the industrial era.
The new record is just the latest to be shattered this year, following a record hot June, July and summer overall, and record hot September in the UK.
Scientists are pointing the finger primarily at climate change, and warned of worse to come. But they also put it down to a warm weather pattern called El Nino, and natural changes in the weather.
The Copernicus Climate Change Service (C3S) confirmed today that in September average surface air temperatures globally reached 16.38C.
The figure is 0.93C above the average for September during the last two decades, and a significant 0.5C warmer than the previous warmest ever September, in 2020.
The margin has astonished scientists.
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Image: Record heat in September smashed previous records by a “huge” 0.5C margin
“It’s huge,” said Professor Ed Hawkins, climate scientist at Reading University. “We shouldn’t be breaking records by this amount.”
Piers Forster – the interim chair of the government’s Climate Change Committee but speaking in his capacity as climate change professor at Leeds University – said variations between months each year are usually quite small.
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“Therefore, breaking the previous September record by a whopping 0.5C is crazy and shows something really bizarre is going on,” he said.
Dr Samantha Burgess, deputy director of C3S, said the “unprecedented temperatures” for September broke records by “an extraordinary amount”.
With two months until the next global climate talks, COP28 in Dubai in December, the “urgency for ambitious climate action has never been more critical”, added Dr Burgess.
The sea was hot too
Today’s findings are based on billions of measurements from satellites, ships, aircraft and weather stations around the world.
They confirmed that temperatures on the ocean surface had also soared in September, reaching the second highest ever, behind only August 2023.
Why was September and this summer so hot globally?
Part of the heat has come from a natural switch in the tropical east Pacific around July from a cool El Nina phase to a warm El Nino one, influencing temperatures around the world.
But while a combination of factors are at play, including natural variability from year to year, scientists believe the main cause is climate change.
Prof Forster said: “We think it’s caused by a combination of factors, principally greenhouse gas emissions being at an all time high.”
Global temperatures have warmed by around 1.1C since the pre-industrial era due to human activity, according to UN’s Intergovernmental Panel on Climate Change.
“What we’re seeing this year is there is a bump on top of that,” said Prof Hawkins, which could be “due to other factors such as El Nino or other weather patterns”.
“But the largest component by far is the fact that we have added so much greenhouse gases in the atmosphere from burning fossil fuels.”
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UK climate deaths since 1990
Prof Hawkins said month after month of record heat was not necessarily a sign the climate crisis was accelerating, but a taste of the future under continued global warming.
Extreme weather events this summer – like fires in the Mediterranean, floods in New York or heatwaves in the UK – will become “more frequent and sadly become normal”, he added.
He said climate change is exacerbating flooding because warmer air can hold more water, meaning rainfall is heavier.
It also makes naturally occurring heatwaves even hotter, and it fuels the hot and dry conditions that allow wildfires to spread rapidly, even if the fires were sparked by something unrelated, he added.
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In a stark and direct intervention, Martin Griffiths, the former UN humanitarian chief, has described the situation in Gaza as genocide.
The statement, made during an interview I conducted with Griffiths on The World, marks one of the most pointed accusations yet from a figure known to be deeply embedded in the world of international politics and diplomacy.
“I think now we’ve got to the point this is unequivocal. Of course it is genocide. Just as it is weaponising aid.
“We don’t need to look behind ourselves to see that’s the case. That should encourage us even more because we, of course, all doubted whether it would come to that level of definition.
“We all doubted whether famine is actually there. I think starvation is killing people. That’s bad enough. We don’t have to worry about famine, which is obviously there lurking in the shadows.
“Also, genocide… of course that’s what has happened. We only need to look at the statements made. Prime Minister Netanyahuhas the virtue of being very clear about his objectives.”
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Ex-Israeli aide dismisses genocide claims
His choice of words is extraordinary – not just for its gravity, but because it’s Griffiths who is saying it.
A veteran diplomat with decades of experience navigating complex international crises, Griffiths is known for his calm and thoughtful demeanour – not for inflammatory language.
For him to use the term “genocide” in a television interview signals a significant shift in how some within the international system are now interpreting events on the ground in Gaza – 20 months since Israel launched its war.
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Just weeks earlier, Tom Fletcher, another respected former British ambassador and current UN humanitarian chief, came close to using the phrase during a UN Security Council session.
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He said: “What more evidence do you need now? Will you act decisively to prevent genocide and to ensure respect for international humanitarian law? Or will you say instead: ‘we did all we could?'”
Whilst he stopped short, his tone showed a clear change in how leading international figures now view the direction of Israeli military operations in Gaza; staggering civilian deaths, and the statements made by Israeli officials prosecuting this war.
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Lawyers representing Israel against accusations brought by South Africa to the International Court of Justice last year – accusing its actions in Gaza of amounting to genocide – called the claims “unfounded”, “absurd” and amounting to “libel”.
They went on to say Israel respected international law and had a right to defend itself.
Now 41.2% of Europe finds itself in some form of drought, according to the latest update from the EU’s European Drought Observatory, which covers 11 to 20 May.
It is most acute in pockets of south-eastern Spain, Cyprus, Greece and Albania, where the strongest “alert” category has been issued, as well as parts of Poland and Ukraine.
But broad stretches of northern and eastern Europe through France, Germany, Poland and Ukraine also drying up, sowing concerns about crop yields.
On Thursday, the UK’s Environment Agency officially declared a drought in North West England after river and reservoir levels were licked away by a dry spring.
Image: More than 40% of Europe was in drought as of 11-20 May 2025. Pic: CEMS / EDO
Image: Heat was record high in March in Europe. The image on the right shows the south of the continent was much wetter than average and the north much drier. Source: Copernicus Climate Change Service
Greece tourism is ‘unsustainable’
In Greece, “overtourism” from millions flocking to its beaches adds further pressure to water supplies, said Nikitas Mylopoulos, professor of water resource management at Thessaly University.
“The tourist sector is unsustainable and there is no planning… leading to a tremendous rise in water demand in summer,” he told Sky News.
“The islands have an intense problem of drought and water scarcity.”
Islands like Santorini and Mykonos are now forced to ship in water from Athens or desalination plants to provide for showers and swimming pools. In the past, many residents could make do with local methods like rainwater harvesting.
But agriculture is a far bigger drain on the country’s water, with waste rife and policies lacking, said Prof Mylopoulos.
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‘Tropical nights’ soar in European hotspots
Wildfire season could be ‘particularly difficult’
This year’s hot and dry conditions are also fuelling the risk of yet another fierce wildfire season in Greece.
Last week civil protection minister Ioannis Kefalogiannis warned of a “particularly difficult” summer.
He said a record 18,000 firefighters have been deployed and the drone fleet almost doubled in a bid to combat fires being fuelled by a hotter climate.
Droughts and their causes are more complicated, but scientists at World Weather Attribution say global warming is exacerbating drought in some parts of the world, including around the Mediterranean.
Image: A drought was declared in northwest England on Thursday. Pic: Reuters
The International Hydropower Association said drought and intense rain in Europe are pushing power plants to “operate at the limits of their existing equipment”.
Extreme weather costs the EU about €28.3bn (£23.8bn) in lost crops and livestock per year, according to insurance firm Howden.
Hayley Fowler, professor of climate change impacts at Newcastle University, said: “With global warming, we expect more prolonged and intense droughts and heatwaves punctuated by more intense rainfall, possibly causing flash floods.
“In recent years, we have experienced more of these atmospheric blocks, causing record heat and persistent drought, as well as severe flooding in other locations in Europe.
“Recent months have been no different, with prolonged dry conditions and heatwaves in northern Europe and floods in southern Europe.”
At least 117 people have died and others are still missing after heavy flooding in Nigeria, an emergency official said.
Authorities initially said 21 people had died but this figure has today risen significantly.
Media reports quoting local government officials said a dam collapse has worsened the situation.
Ibrahim Hussaini, head of Niger State Emergency Management Agency, said some 3,000 houses were underwater in two communities.
Videos posted on social media show floodwater sweeping through neighbourhoods, with rooftops barely visible above the brown currents. One clip shows a tanker floating through a town.
Image: A tanker is swept away by floodwaters
The chairman of the Mokwa local government area suggested poor infrastructure has worsened the impact of the flooding.
Jibril Muregi has appealed to the government to start “long overdue” construction of waterways in the area under a climate resilience project.
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Image: Water appears to be flowing over a dam behind the town
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In a similar occurrence last September, torrential rains and a dam collapse in Nigeria’s northeastern Maiduguri caused severe flooding, leaving at least 30 people dead and displacing millions.
Nigeriais prone to flooding during the rainy season, which began in April – and flooding is becoming more common and extreme as the climate warms.
Hotter air is thirstier and can hold more moisture – about 7% more for every 1C warmer – meaning it unleashes heavier flooding when it rains.
Violent rain, which killed hundreds of people in Nigeria during 2022, was made at least 80 times more likely and 20% more intense by climate change, analysis by World Weather Attribution found.