How Hot Can It Get?

The vexed history of the world extreme heat record

Death Valley, California, near Furnace Creek, August 2010 (author’s photo)

Western North America has been having an unusually hot summer. On Friday, 9 July 2021, the mercury at Furnace Creek in Death Valley, California, hit 130ºF (54.4ºC). This temperature has been previously been recorded once before, in August 2020. If accurate, it might be the highest temperature measured on Earth in recorded history. We say might, because the global extreme temperature record has a usually troubled history.

Creating the World Temperature Record

Dutch scientist Daniel Gabriel Fahrenheit invented the mercury thermometer in 1714, and soon after, came up with a scale for measuring temperature which (slightly modified) bears his name today. The systemic building of weather stations and keeping of temperature records began in the nineteenth century. Early weather stations, however, were set up inconsistently and so produced inconsistent measurements. To correctly measure the air temperature, a thermometer needs to be shaded and placed over a non-reflective surface, like soil. So, from the mid-nineteenth century onwards, meteorologists began placing thermometers inside little shelters surrounded by louvered screens and built over soil or grass, allowing air to circulate but keeping them out of the sun. For a standard measurement, the thermometer needs to be 1.5 metres (4’11”) above the ground.

Modern temperature records date from the enclosure of thermometers and the adoption of standard measuring practices. U.S. temperature records, for example, begin in 1880, even though individual American sites may have reliable records from earlier.

Of course, not all readings captured since the 1880s are reliable. Many were taken from improperly-housed thermometers by untrained observers in isolated weather stations where there was no one to double-check and no nearby stations to compare results with. The weather record is littered with incredible readings, particularly from the early twentieth century.

For this reason, there has been an ongoing debate on what the highest temperature ever recorded on earth is (the lowest temperatures on earth have all been recorded on the Antarctic Plateau using modern scientific equipment by trained observers and are not in…