Global temperatures were so high in September that one climate scientist has described the situation as “absolutely gobsmackingly bananas.”

“The first global temperature data is in for the full month of September. This month was, in my professional opinion as a climate scientist – absolutely gobsmackingly bananas,” Zeke Hausfather of the Berkeley Earth climate data project wrote on X, formerly known as Twitter.

Records were broken in September, the data show. August and July were also the hottest ever, with July the hottest month since pre-industrial times.

Last month beat the records for previous Septembers by 0.5C, which the Guardian said was the largest jump in temperature ever. In fact, September was about 1.8C warmer than pre-industrial levels.

The climate crisis is contributing, as is the natural weather trend El Nino, which heats the Pacific.

This year is expected to be the hottest year ever, and 2024 may be worse, said scientists because El Nino effects are usually the greatest the year after.

This summer has been wildfires in Europe, and extreme heat in Brazil and deadly flooding in Libya – after torrential rain caused two dams to burst – that may have killed thousands.

Other less extreme factors may include an increase in the 11-year solar cycle, reductions in sun-blocking sulphur emissions from shipping and industry, and a volcano erupting in Tonga, according to Hausfather.

Mika Rantanen, of the Finnish Meteorological Institute, commented on X: “I'm still struggling to comprehend how a single year can jump so much compared to previous years. Just by adding the latest data point, the linear warming trend since 1979 increased by 10%.”

Professor Ed Hawkins, at the University of Reading, UK, told the Guardian that the heat this last summer was “extraordinary” and he echoed Rantanen: “I’m still struggling to comprehend how a single year can jump so much compared to previous years.”

The unprecedented temperatures for the time of year observed in September have broken records by an extraordinary amount, according to Samantha Burgess of the Copernicus Climate Change Service of the EU.

"2023 [is] on track to be the warmest year and about 1.4C above pre-industrial average temperatures," Burgess said. "Two months out from COP28 [the UN climate conference in the UAE], the sense of urgency for ambitious climate action has never been more critical.”

Friederike Otto, senior lecturer in climate science at the Grantham Institute for Climate Change and the Environment in the UK said “temperature records continue to be broken because we have not stopped burning fossil fuels. It is that simple.

“People and ecosystems are dying.”

“The significant margin by which the September record was broken should be a wake-up call for policymakers and negotiators ahead of COP28,” Otto added. “We absolutely must agree to phase out fossil fuels.”