World Record Temperature Not So Hot Anymore

Blame it on a bad thermometer and a novice observer.

For 90 years, that combination had the world believing the hottest temperature ever recorded in a populated spot on Earth was 58 C (136.4 F) in El Azizia, Libya, on Sept. 13, 1922. But no more — Death Valley, Calif., with a 56.7 C (134 F) reading recorded on July 10, 1913, is the newly crowned King of Heat.

The confusing Six-Bellani thermometer implicated in the false 1922 Libyan reading (image via Library of the Observatorio Astronomico Di Palermo)

That’s the ruling of the World Meteorological Organization, after a long investigation that was interrupted and imperiled by the Libyan revolution. “We found systematic errors in the 1922 reading,” said Randy Cerveny, a professor at Arizona State University, keeper of the WMO Archive of Weather and Climate Extremes.

A careful review of the logs from back in 1922 backed up the theory that an antiquated device – even by the standards of the day – was at the root of the problem with the Libyan reading.

“One of the problems with a Six-Bellini (sic) thermometer is that the indicator—the pointer—to the temperature scale could conceivably be read at the top of the pointer or the bottom of the pointer,” Cerveny said. “If an inexperienced observer used the top of the pointer rather than the bottom, he would have been as much as 7 C in error.”

Adding to the evidence that the 58 C temperature was bogus: It didn’t fit with other readings in the area or the readings that came afterward at the military base site.

The WMO probe got under way in 2010, and the Libyan revolution began to unfold in early 2011. The Libyan meteorological official on the investigating team, Khalid El Fadli, disappeared in the chaos, putting the search for an answer on hold for months.

“Khalid El Fadli did this at great risk to himself,” Cerveny said. “He was an official of the previous regime, so when the revolution began to turn, his safety was a key concern.”

A PDF of the full report on the investigation into the hottest temperature record is available on the website of the American Meteorological Society.

Pete Danko is a writer and editor based in Portland, Oregon. His work has appeared in Breaking Energy, National Geographic's Energy Blog, The New York Times, San Francisco Chronicle and elsewhere.