The BoM went public in December 2011 saying it was the hottest year ever in Perth. This press was followed up with their page spelling out the BoM case. I noticed the BoM said little about any stations except Perth Metro – it is well known around climate people that the Perth recording site has moved a few times since the late 19th Century. I have had a quick look to see if 2011 was the hottest year ever in stations near Perth. Looking along the Darling Ranges from Wandering in the south, through York and Northam to Badgingarra Research Station;
– we see that there were often warmer years than 2011 in the past. So I assume that either the Perth Metro data is not being correctly compared to past years – or the “hottest year” in Perth that the BoM claims – is more of a local effect than the BoM hopes for.
Interesting to note high temperatures in Perth around 1974 when there were floods in Queensland and Brisbane in particular. 2011 had floods in Queensland and Brisbane area (although partly man caused due to stupid strategy).
Yesterday, heard that Mt Isa had the coldest January day on record, also floods again in parts of Queensland
Warwick
O/T but this might be of interest. clivebest.com/blog/?p=3075
He has generated a Flash graph (world map) showing the sites used by HADCRU3V database, including the 1860 figures.
Well known sites in 1860 – Adelaide, Sydney and Hobart airports. Perth (any Met Office there in 1860?), Melbourne, Bathurst and the University of New England in Armidale. Surely this is a mistake or rather several mistakes.
The East Perth location of the official Perth site before 2004 is across the road (about 20 meters) from a large grassed park that is irrigated every night in summer. The 2004 move to an unirrigated location at Mt Lawley resulted in an approx 1.5C fall in nighttime temperatures.
From your link,
The average annual minimum at 9225 over the past 17 years was about 1.6C cooler than it had been at 9034, the drop happening immediately the station change was made. Maybe a rapid onset of global cooling, but a more robust explanation is that the four kilometre change in station locations significantly affected temperature recordings and made historic pre-1994 comparisons dubious at best and irrelevant at worst.
Nighttime irrigation causes a near ground greenhouse warming effect.
The new Mt Lawley location is in middle of field of bare earth (sand), which will reflect more heat than grass, heating up the Stevenson screen nicely during the day.
I’ve updated and re-crunched some data from the Ag Dept for Medina station and posted an article on my blog, pointing to this one.
Medina is on the coastal plain, a little South of Perth and well within the metropolitan area. Using daily maxima, an eyeball of the graph tells me that it was warmer in at least 6 out of the 10 previous years.
I’ve now managed to make 2011 the hottest year ever, using the recipe cooked up by BoM and updated my blog post.
You take your daily extreme (max temperature) and average them over a year. Pay no heed to what you are doing; that it makes little to no sense; just do it and enjoy the result.