As thousands of tourists fled wildfires this week on the Greek island of Rhodes, and many more suffered baking heat across the US Southwest, they were doing so during what scientists now say is the world’s hottest month on record.

An analysis by Germany’s Leipzig University released on Thursday found that July 2023 will shatter heat records, with this month’s mean global temperature projected to be roughly 1.5 degrees Celsius (2.7 Fahrenheit) above the pre-industrial mean.

This would be at least 0.2C (0.4F) warmer than July 2019, the former front-runner in the 174-year observational record, according to European Union data.

The margin of difference between now and July 2019 is “so substantial that we can already say with absolute certainty that it is going to be the warmest July,” Leipzig climate scientist Karsten Haustein said.

Michael Mann, a climate scientist at the University of Pennsylvania, said it was clear by mid-July that it was going to be a record warm month, and provided an “indicator of a planet that will continue to warm as long as we burn fossil fuels”.

Normally, the global mean temperature for July is around 16C (61F), inclusive of the Southern Hemisphere winter. But this July it has surged to near 17C (63F).

What’s more, “we may have to go back thousands if not tens of thousands of years to find similarly warm conditions on our planet,” Haustein said. Early, less fine-tuned climate records — gathered from things like ice cores and tree rings — suggest the Earth has not been this hot in 120,000 years.

Haustein’s analysis is based on preliminary temperature data and weather models, including forecast temperatures through the end of this month, but validated by unaffiliated scientists.

The U.N. World Meteorological Organization (WMO) also said on Thursday it was “extremely likely” July 2023 would break the record, but would not call it outright, instead waiting until the availability of all finalised data.

“July is almost certainly the hottest month in the instrumental record,” said Piers Forster, a climate scientist at Leeds University in Britain. “The result is confirmed by several independent datasets combining measurements in the ocean and over land. It is statistically robust.”

Hothouse planet

Sweltering temperatures have affected considerable swathes of the planet. While night-time is typically cooler in the desert, Death Valley in the US state of California saw the hottest night ever recorded globally this month.

Temperatures in a northwest China township soared as high as 52.2C (126F), breaking the national record.

Canadian wildfires burned at an unprecedented pace. And France, Spain, Germany and Poland sizzled under a major heatwave, with the mercury climbing into the mid-40s on the Italian island of Sicily, part of which is engulfed in flames.

This is “the harsh reality of climate change and a foretaste of the future,” said WMO Secretary-General Petteri Taalas.

The ocean, too, is in hot water.

Marine heatwaves have unfolded along coastlines from Florida to Australia, raising concerns about coral reef die-off.

Even one of the coldest places on Earth - Antarctica - is feeling the heat. Sea ice is currently at a record low in the Southern Hemisphere’s winter - the time when ice should soon be reaching its maximum extent.

Meanwhile, record rainfall and floods have deluged South Korea, Japan, India and Pakistan.

“Global mean temperature (itself) doesn’t kill anyone,” said Friederike Otto, a scientist with the Grantham Institute for Climate Change in London. “But a ‘hottest July ever’ manifests in extreme weather events around the globe.”

The planet is in the early stages of an El Nino event, borne of unusually warm waters in the eastern Pacific. El Nino typically delivers warmer temperatures around the world, doubling down on the warming driven by human-caused climate change, which scientists said this week had played an “absolutely overwhelming” role in July’s extreme heatwaves.

While El Nino’s impacts are expected to peak later this year and into 2024, it “has already started to help boost the temperatures”, said Haustein.

Scientists expect 2023 or 2024 will end up as the hottest year in the record books, surpassing 2016.