The Earth has had the hottest September on record – and by a record-breaking margin, the World Meteorological Organisation (WMO) has said.
“This continues an extended streak of extraordinary land and sea-surface temperatures and is an ominous signal about the speed with which greenhouse gases are changing our climate,” the WMO said on Thursday.
The unprecedented jump in global temperatures during last month has been confirmed by reliable data sets across the planet. This year is on track to be the warmest on record, with numerous high temperature records broken in recent months.
The EU’s Copernicus Climate Change Service stated that September had an average surface temperature of 16.38 degrees, 0.5 degrees above the previous warmest September, in 2020.
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This is the result of continuing high levels of carbon emissions combined with a rapid flip of the planet’s biggest natural climate phenomenon, El Niño. The previous three years saw La Niña conditions in the Pacific Ocean, which lowers global temperature by a few tenths of a degree as more heat is stored in the ocean.
It follows the hottest August and hottest July, with the latter being the hottest month recorded.
A total of 14 weather stations across Ireland broke their September maximum temperature records last month with 10 stations breaking their September highest minimum temperature.
Irish climate scientist Prof Peter Thorne of Maynooth University said the September record “was mind-bogglingly huge” when temperature records were usually a matter of hundredths of a degree rather than “a whole half of a degree”.
“This is weather that globally we have not experienced in at least thousands of years,” he said.
The world was heading to this scenario on a permanent basis unless it reduced human-induced greenhouse gases, Prof Thorne said.
It was yet another warning “in a sorry litany of warnings” to politicians worldwide and to others that emissions were rising, yet they were still making “decisions that are counter intuitive to what is happening”, he said.
There was a misguided belief that temperature increase would be linear and somehow manageable, but this was not the case as impacts would be a lot worse with every increase in warming, he said. “We need to be shaken out of that mistaken belief.”
“This will get a lot worse. We need to double down and double down again until we have the job done,” Prof Thorne said.
“September’s weather has been, literally, off the charts. But while we in Ireland are experiencing these records as warm and pleasant temperatures, elsewhere higher temperatures will manifest as destruction and disaster. We’ve already seen the effect of wildfires, floods and heat in European countries this summer, and the scientific prognosis is that it will get worse,” said Friends of the Earth senior climate adviser Sadhbh O’Neill.
She said: “The only antidote to the ‘climate hell’ that UN secretary general António Guterres has been warning about is to stop burning fossil fuels. The forthcoming Cop in UAE [the annual global climate negotiations of parties to the UN] needs to be ‘the fossil fuel Cop’. It’s not going to be enough for it to agree on new renewables targets: we need a clear commitment to phase out fossil fuels and a requirement on parties not to add new fossil fuel infrastructure.”
High temperatures have driven extreme weather events, notably heatwaves, wildfires and flash floods across the world.
“Since June the world has experienced unprecedented heat on land and sea. The temperature anomalies are enormous – far bigger than anything we have ever seen in the past. Antarctic winter sea ice extent was the lowest on record for the time of year,” said WMO secretary general Prof Petteri Taalas.
“What is especially worrying is that the warming El Niño event is still developing, and so we can expect these record-breaking temperatures to continue for months, with cascading impacts on our environment and society,” he predicted.
“September was, in my professional opinion as a climate scientist, absolutely gobsmackingly bananas,” said climate scientist Zeke Hausfather of Berkeley Earth climate data project in the US.
“Observations of Australia’s climate in September are shocking. Figures show where maximum temperatures were the highest on record, with many areas 3-5 degrees above average. Rainfall deficits are primed for drought. Summer is going to be brutal,” said scientist Joelle Gergis.
In August, the Guardian asked 45 leading climate scientists for their assessments. The predominant view was, despite it certainly feeling as if events had taken an alarming turn, the broad global heating trend seen to date was entirely in line with 30 years of scientific predictions.
Increasingly severe weather impacts had also been long signposted by scientists, though the speed and intensity of the reality and the unexpected vulnerability of many populations scared some. The off-the-charts sea temperatures, especially in the Atlantic and Antarctic sea ice loss were seen as the most shocking events.
They predicted the exceptional events of 2023 could be a normal year in just a decade, unless there was a dramatic increase in climate action. The researchers overwhelmingly pointed to one action as critical: slashing the burning of fossil fuels down to zero.
Meanwhile many parts of the world have experienced prolonged heatwaves which in some instances were in excess of 45 degrees; far beyond the limit for human survival. In Ireland, summer months had exceptional amounts of rainfall. – Additional reporting: Guardian
