Joanne Nova has posted data from Ian Hill on extreme heatwaves in Adelaide, Australia. To quote

It’s another mindless record used to remind the public to “keep the faith” and recite the litancy:

“Adelaide had it’s hottest start to the year since 1900″ Sky news

Picking three particular days out of 365 and comparing them over a century is about as cherry-pickingly meaningless as it gets. But Ian Hill went back through the records to find that not only have there been 79 heatwaves in Adelaide since 1887, but there have been 51 heat-waves that were hotter since 1887.

I have done a bit of number crunching of my own, that is quite revealing. Higher temperatures are meant to lead to more extreme heatwaves. Using Ian Hill’s figures Adelaide is providing an exception. Hill’s definition of a heatwave is 3 or more consecutive days where the maximum temperature exceeds 38^oC. I have downloaded the figures and categorised by decade. There are two ways I have analysed this data. First is by the number of heatwaves per decade. Second is the number of days per decade.

There are a number of points.

1. The temperature data only starts in 1887, so the 1880s are probably more significant.
   
2. The current decade might be more significant.
   
3. Last decade, beginning 2000 was no more significant than the decades 1890s, 1900s, or 1930s.
   
4. The 1990s was no more significant than the decades 1910s and 1920s
   

Is there, however, a revival of extreme heatwaves in the last twenty years?

Nope. Just a couple of extreme years in 2008 and 2009.