Posted on behalf of Michele Catanzaro.
The world’s highest temperature ever recorded has fallen from 58 °C (136.4 °F) to 56.7 °C (134 °F), after a World Meteorological Organization (WMO) assessment, published on 13 September, showed that the previous record was a mistake. As a consequence, the hottest spot ever measured has moved from Libya, where it has been believed for the past 90 years to be, to Death Valley in California.
The long-lasting mistake is due to an incorrect measurement performed on 13 September 1922 by an inexperienced member of the Italian military in El Azizia, approximately 40 kilometres south–southwest of Tripoli, according to the study. A WMO committee found that the military used a problematic instrument (a Bellani-Six thermometer) in non-standard conditions (on asphalt instead of on sand). As a result, the record does not match the temperatures observed at the same time in nearby locations, and successively at the same site.
The record for the next-hottest spot is held by a measurement performed at Greenland Ranch in Death Valley on 10 July 1913. “Available evidence supports the validity of this measure,” says Randall Cerveny, WMO rapporteur of weather and climate extremes, and head of the committee that examined Libya’s evidence. “However, there are undoubtedly places with hotter temperatures: here we are comparing only places where standardized measurements have been done,” he points out.
A 2010 blog post by meteorology writer Christopher Burt raising doubts about the 1922 measurement first brought the issue to Cerveny’s attention. Cerveny formed an international commission that included two representatives from Italy (Libya’s colonizer in 1922) and one from Libya to examine the evidence. They concluded that the 1922 measurement was an error.