Facebook posts shared tens of thousands of times claim that Australia's hottest recorded temperature was 53.9 degrees Celsius (129 Fahrenheit) in the 1820s, implying that this is evidence against human-driven climate change in recent decades. This is misleading; meteorologists say the reading cannot be compared with today's records, given the standard of equipment used at the time and the sparseness of measurements. Isolated temperatures do not represent a climate trend and the heating over recent decades is well documented.
"The hottest day on record? Not 2010, BUT 1828 at a blistering 53.9 °C," reads a Facebook post shared 70,000 times since January 9, 2016.
"We are told today's climate has more records and more extremes than times gone by, but the few records we have from the early 1800's are eye-popping. Things were not just hotter, but so wildly hot it burst thermometers," adds the post, which was widely shared in recent months.
"The earliest temperature records we have show that Australia was a land of shocking heatwaves and droughts".
Screenshot of a Facebook post sharing the misleading claim, taken on September 7, 2022
It is not clear why the post refers to 2010 -- that year does not feature on a list of record temperatures published by the Australian Bureau of Meteorology (BOM).
Citing Sturt's journals, the blog entry gives the "record" as the 129 degrees Fahrenheit (53.9C) in the shade that he recorded in December 1828, though higher measures on other dates are also cited. One of the journal entries quoted describes a thermometer bursting after the heat passed its maximum reading of 127F.
The BOM said those records are not part of its official series and that the 1828 measurement could not be verified.
"Climate observations prior to 1910 were limited across the Australian continent, being concentrated mostly around settlements and in eastern Australia," a BOM spokesperson told AFP.
"There is little information available regarding the types of instruments used, their calibration and exposures. This makes it difficult to align these early-era observations with the official record that commenced in 1910."
The bureau's climate data series of reference, ACORN-SAT, is based on observations going back to 1910 and is complete enough to compare temperature records over time.
"There is no known information about whether the instrument used for this measurement was protected from the sun and it is extremely unlikely that it was taken in any kind of shelter," the BOM spokesperson said.
"Therefore, the observations from the expedition cannot be directly compared with those from the more recent observation network."
The bureau measures temperatures using a Stevenson screen, a slatted box invented in the 1860s to shelter thermometers from direct sunlight on all sides while allowing them to measure the air temperature. Before that, a different kind of shelter was used: a Glaisher stand, which was covered from above but not on the sides or below and therefore left the thermometer exposed to more light.
In a 60-year comparison of the two sheltering devices in Adelaide, the Glaisher stand was found to give higher average maximum temperatures than the Stevenson screen – about 1C higher, according to the BOM.
Weather vs climate
Individual daily temperatures are weather events whereas climate change is measured by observing changes in average conditions over longer periods of time. NASA gives an explanation here.
The left-hand chart shows temperatures rising sharply from 1850 onwards. On the right-hand chart, the bottom blue line shows how much lower global temperatures would be without the impact of humans releasing greenhouse gases by burning fossil fuels.
IPPC chart on left shows sharp temperature rise post-1850 - the biggest rise in 2,000 years
Australia's highest officially recorded temperature was 50.7C (123.3F) on January 2, 1960 at Oodnadatta Airport in South Australia. That record was matched in January 2022 at Onslow in Western Australia.