- JoNova - https://joannenova.com.au -

Not the hottest ever summer for most Australians in Sydney, Melbourne or Brisbane. Not “extreme” heatwaves either.

Despite the wild hype about records being broken, and how hot this summer has “felt” for most Australians there have been many hotter summers, and for millions of people this summer was not remarkable at all.

The BOM is planting the unscientific suggestion it “felt warm” when thermometers in most major centres tell us it was just summer. The population of Sydney, Brisbane and Melbourne combined is almost 11 million. Nearly 50% of all Australians experienced an average to above average summer, but none of them experienced an extreme summer or a record hot season.

Since there are 100 different ways of measuring a “record”, could it be the BOM is cherry picking whatever record it can find, but ignoring all the non-records, the average measurements, and the ordinary heat?

Melbourne, hot but not extreme

In Melbourne there have been nine hotter summers, and two of those were more than a century ago. Those summers weren’t just a bit hotter. It was nearly a whole degree hotter (as an average of maximum summer temperatures) in 1898 and 1951.

In Melbourne this summer qualifies as the tenth hottest. It was far hotter in 1898, 1951, 1981, and 2001


Much of the upward rise in Melbourne could be due to the Urban Heat Island Effect (UHI). Compare the slope of Melbourne temperatures to the country surrounding it. See John McLean’s page on UHI in Melbourne. (H/t to Warwick Hughes for the UHI point)

Credit to John McLean for this graph.

In the BoM’s own words:
“That the overnight temperatures in Melbourne are higher than those in most surrounding localities is a consequence of the city being under the influence of the effect of urbanisation (cities are usually warmer than their rural surroundings, especially at night, because of heat stored in bricks and concrete and trapped between close-packed buildings).”


Sydney had two hot days in an ordinary summer

In Sydney there have been 18 or more summers that were hotter than this one.

Sydney may have scored it’s hottest day ever, but it hasn’t been an extraordinary summer at all.

In Sydney there have been 20 or more summers that were hotter than this one.


There were not many extreme hot days either in Sydney and Melbourne

The way the BOM describes it, this summer was packed with extreme heat. Instead, compared to the last 150 summers, there was nothing that unusual about summer in Sydney or Melbourne. The BoM has nominated 37C as its line in the sand for new records this past summer, so let’s dig through the history books to compare that particular temperature.


In Sydney, there were two hot days this summer. That’s normal. | Graph thanks to Chris Gillham.

In Melbourne, 2013 had a very ordinary number of hot days compared to past years.  | Graph thanks to Chris Gillham.


Brisbane had an average summer – where are the headlines?

In Brisbane the summer mean was 28.92 C, barely 0.05 above the average of 28.87 C.  Both round to 28.9C, so Brisbane’s summer was absolutely…. average. (Thanks to Ken Stewart for that).

Thanks to Chris Gillham for the line graphs.

What does it mean?

There is no denying it was hot in some parts of Australia this summer, and may have been extreme, though that is certainly not true for the parts where most Australians live. But whether the nation as a whole experienced record heat depends on how its measured, and as I’ll post tomorrow, the “average” of a whole continent can be measured many different ways with many different data-sets.

Why is the BOM seeking headlines and declaring records, when the data-set and methods are so unfinished they have not been released publicly? (Plenty of errors and flaws and mysterious adjustments have been found in past sets.) Why is the BOM focused on one season, or a few weeks of heat, when it’s only the long term trends that matter (as they remind us whenever it’s cold)? Why won’t the BOM announce how temperatures are averaged and measured before they announce the records?

Why are the BOM seeding the idea that this summer “felt” hot to Australians when it’s not just unscientific, but incorrect?

Why do they focus on one hot day in Moomba, when the records there are so short they would have missed all the previous hot spells? Those previous hot spells broke the Moomba records over and over and a long time ago.

In the end, even if it was a record hot summer, that doesn’t mean CO2 caused any of it. The world has been warming for 300 years. The world has been warmer before. None of that was connected to CO2 levels.


8.7 out of 10 based on 92 ratings