At the beginning of each new year, we are encouraged to make some new resolution, or other. The idea is usually to seek to improve on our current situation through a worthy intent. However, intent can be the enemy of truth,because too often it provides a goal, without the discomfort of proper analysis – or even honest reflection.
Also, at the beginning of each new year the Australian Bureau of Meteorology publishes their annual climate statement. For at least the past decade the intent has been to emphasise that the Earth is warming – and it’s our fault.
Of course, there is no one place in Australia where the mean temperature of the continent can be measured; so the Bureau relies on a reconstruction to determine how hot last year was, relative to the historical record. Their method, however, is subjective. They neither simply combine all the temperature series and just provide us with the overall average for each year, nor do they choose a subset based on the most complete and longest records. Rather they have a somewhat contrived method, full of intent and post-truth science. I’ve written about this extensively, but my concerns are dismissed – not on the basis of rational argument, but on the authority of the institution that is the Bureau of Meteorology.
When all 1,655 maximum temperature series for Australia are simply combined, and truncated to begin in 1910 – thus avoiding problems of equipment change associated with Stevenson screen installations – the hottest years are 1980, 1914, 1919, 1915 and 1940, respectively. A linear trend line through this reconstruction gives a rate of warming of 0.4 degree Celsius per century – less than half that reported by the Bureau.
I’m still working-up my reconstruction for the entire continent based on just the longest and highest quality temperature series.
Late last year, I had a book chapter, co-authored with John Abbot and published by Elsevier, which shows historical temperature trends just for south-east Australia from 1887 – based on the longest, continuous, highest quality temperature series just for this region.
In the chapter we conclude that temperature trends for south-east Australia are best described as showing statistically significant cooling (yes cooling) of 1.5 degree Celsius from 1887 to 1949, followed by warming of nearly 2 degrees Celsius from 1950 to 2013. The warmest year in this reconstruction is 2007, followed very closely by 1914.
A colleague at the University of Tasmania, Jaco Vlok, has compared our south-east reconstruction with a reconstruction based on all 289 temperature series for Victoria – but only from 1910. There is a very high degree of synchrony between the reconstructions, though when all the raw data is simply combined – Vlok’s approach – the hottest years are all in the earlier part of the record: 1914 (hottest) followed by 1919, 1921, 1938, 1961 and then 2014.
Considering land temperature across Australia, 1914 was almost certainly the hottest year across southern Australia, and 1915 the hottest across northern Australia – or at least north-east Australia. But recent years come awfully close – because there has been an overall strong warming trend since at least 1960, albiet nothing catastrophic.
If we consider hottest months (rather than whole years), then the hottest January was perhaps 1896 – when people were evacuated from places like Bourke in western NSW. The hottest summer was perhaps in 1938-39; at Rutherglen in Victoria this summer was a full 2°C hotter than the ten most recent summers – including the last summer of 2015-16. Indeed, there is nothing unprecedented about recent temperatures in Australia.
One of my new year’s resolutions is to spend more time understanding why this is so: why we choose to have such a negative and contrived relationship with this important aspect of our natural history – the historical temperature record for Australia.
This article originally appeared in the Online Opinion