By Paul Homewood
This made news a couple of weeks ago, but I have been waiting for full details from the BOM:
Australia has experienced its hottest summer on record, according to the nation’s Bureau of Meteorology.
Hundreds of individual heat records were shattered across the country over the past three months.
The warm weather, 2.14C above the long-term average, caused bushfires, blackouts and a rise in hospital admissions.
Wildlife also suffered, with reports of mass deaths of wild horses, native bats and fish.
"The real standout was just how widespread and prolonged each heatwave was – almost everywhere was affected," climatologist Blair Trewin told the BBC.
Temperatures had exceeded the previous hottest summer in 2012-13 by nearly 1C, he added – "a very large margin for a national record".
Naturally the Australian Bureau of Meteorology has blamed it on climate change. But is it quite as simple as that?
Nationally, summer mean temperatures have been about a degree higher than the previous record, as have average daily maximums. On the face of it, that does seem extraordinary.
However, the BOM records only start in 1910, and we know there were severe heatwaves prior to that. So let’s take a closer look at NSW, which also broke the record by a long way this year:
One of the longest running temperature records in NSW comes from Walgett, a tiny town in the interior, where temperature measurements date back to 1878. Even now, Walgett is pretty much unaffected by UHI, so long term trends are far more reliable than many other sites.
When we examine the full period of record, a totally different picture emerges:
Far from this year being the record, the hottest summer was actually back in 1900. This summer only ranks 5th, behind 2017, 1902 and 2006.
The summers of 1884 and 1901 are also close behind.
In fact, the spate of hot summers recently look little different to those of the early 1900s.
On a monthly basis, the only month which broke the record in NSW was January.
Yet even this month was not exceptional at Walgett, where the hottest January was in 1882:
A comparison of the daily temperatures in 1882 and 2019, shows that the former were much more extreme, with a high of 47.8C. By contrast the highest this January was 46.4C:
The all-time high for any month at Walgett is 49.2C, set in January 1903.
The BOM don’t like people knowing about those heatwaves prior to 1910. They claim that measurements were unreliable before then, yet much prefer to continue using data from the middle of big cities such as Sydney and Melbourne.
Whether older temperature measurements from the likes of Walgett are a tenth of a degree or so out, it is indisputable that those heatwaves did occur, and were extremely severe, as many accounts at the time testify.
The weather station at Walgett was situated within the town until 1993, when it was switched to the airport, a short distance away.
There was one month overlap, during which the airport temperatures registered 0.5C lower, seemingly indicating the UHI effect of the old site at the Council Depot.
This is in spite of the fact that Walgett is still only a tiny town, with a population of 2267.
What is clear though is that the Walgett of the 19thC, little more than a collection of wooden shacks, would not have had the same UHI effect as today with roads, houses and air conditioning.
In other words, old Walgett is not an unreasonable comparison with the new airfield site, as far as UHI is concerned.
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March 13, 2019 at 12:06PM