Last month was the hottest September on record, with an average global temperature of 61.48 degrees. The mark comes on the heels of the hottest July and August ever recorded, according to the European Union’s Copernicus Climate Change Service.
While July and August had hotter raw temperatures because they are warmer months on the calendar, September had what scientists call the biggest anomaly, or departure from normal. Temperature anomalies are crucial pieces of data in a warming world.
September’s average temperature was 1.7 degrees Fahrenheit above the 1991-2020 average for September. That’s the warmest margin above average for a month in 83 years of records kept by the European Space Agency’s Copernicus Climate Change Service.
“It’s just mind-blowing, really,” said Copernicus Director Carlo Buontempo. “Never seen anything like that in any month in our records.”
The leap is so profound that Zeke Hausfather, the climate research lead for the financial services company Stripe took to X, formerly known as Twitter, and wrote, “This month was, in my professional opinion as a climate scientist — 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. JRA-55 beat the prior monthly record by over 0.5C, and was around 1.8C warmer than preindutrial levels.
— Zeke Hausfather (@hausfath) October 3, 2023
“This extreme month has pushed 2023 into the dubious honor of first place — on track to be the warmest year and around 1.4°C above pre-industrial average temperatures,” said Samantha Burgess, deputy director of Copernicus on the organization’s website.
South Florida was part of the trend. NOAA data shows that South Florida had an anomalously hot September, with 27 out of 30 days in the month above the “normal” temperature range for our region. October is looking just as abnormal. Thursday was the hottest October 12 on record for South Florida, at 93 degrees, and Friday broke records in Miami, with 95 degrees and Fort Lauderdale at 93 degrees.
The Copernicus report showed that average sea surface temperatures globally were the warmest on record for September, and the second warmest for any month, only behind August 2023.
The hot September fits a larger trend. According to NOAA, the 10 warmest years in the historical record have all occurred since 2010.
Of the 30 hottest months recorded since 1940, all are June, July and August, with one exception, September of 2023. The hottest two months of the lot were July and August of 2023.
There were some areas of the globe that were cooler than normal. They include western parts of the U.S., Libya, which was soaked with heavy rains, southern Greenland, and the far south of South America and Africa.
The hot temperatures stretched across the globe but they were chiefly driven by persistent and unusual warmth in the world’s oceans, which didn’t cool off as much in September as normal and have been record hot since spring, said Copernicus Director Carlo Buontempo.
The hottest year on record is 2016, which was an El Niño year just like 2023. El Niños generally cause warmer temperatures globally and are a natural cyclical occurrence.
Typically, east-to-west trade winds over the Pacific Ocean push hot surface water west, toward Asia, and cause an upwelling of cool water along the South American coast. When the trade winds dissipate in El Niño years, that hot surface water piles up along the South American coast and affects weather globally.
One effect is warmer global temperatures.
Though El Niño is playing a part, climate change has a bigger footprint in this warmth, Buontempo said.
“What we’re seeing right now is the backdrop of rapid global warming at a pace that the Earth has not seen in eons coupled with El Niño, natural climate cycle,” said U.S. climate scientist Jessica Moerman, who is also president of the Evangelical Environmental Network. “This double whammy together is where things get dangerous.”
Reporting from The Associated Press contributed to this news article.
This story was produced in partnership with the Florida Climate Reporting Network, a multi-newsroom initiative founded by the Miami Herald, the South Florida Sun Sentinel, The Palm Beach Post, the Orlando Sentinel, WLRN Public Media and the Tampa Bay Times.
