Australia recently endured it’s warmest day ever and a heatwave that covered the country. The BOM released a statement with some basic statistics.
For September to December (i.e. the last four months of 2012) the average Australian maximum temperature was the highest on record with a national anomaly of +1.61 °C, slightly ahead of the previous record of 1.60 °C set in 2002 (national records go back to 1910).
Australia set a new record for the highest national area-average temperature, recording 40.33 °C and surpassing the previous record set on 21 December 1972 (40.17 °C). To date (data up to the 8 January 2013) the national area-average for each of the first 8 days of 2013 have been in the top 20 hottest days on record, with 8 January the third hottest on record and the first time 7 consecutive days over 39 °C has ever been recorded for Australia.
Joanne Nova responds by saying there’s nothing special going on. That’s climate denial for you.
Nova says “So what? This is not an unusual heat-wave” , then presents a map of Australia showing 20 “record maximums”.
As usual, Nova’s argument has a few problems …
- an individual record set at one location is NOT the same as having a heatwave that covered the nation.
- 5 of the temps are from 1970 onwards.
- 10 temperatures were prior to 1910 using equipment that allowed influence from ground radiation, recording temperatures higher than modern equipment.
- early explorers’ thermometers have not been calibrated against the modern thermometer, but Nova assumes there won’t be much difference.
- early explorers’ techniques for recording temperatures did not shield from nearby radiation sources and did not measure the same metric as current equipment.
BOM’s “Excuse” for “deleting” some long held temperature records
Nova says “The Stevenson Screens were in fact designed to try to replicate the conditions in which they had been measuring temperature already in most cases. So unless it was clearly documented that the method prior to the installation of the Stevenson Screen was deficient, there would be no reason to disregard the earlier records from the BOM records.“
But as usual, Nova is ill-informed. People have looked at the difference between older equipment and modern Stevenson Screen and the reason for discarding old data is because of the warming bias and unreliable results of the older data.
The modern Stevenson Screens were phased in between 1880 and 1910, prior to that Greenwich or Glaisher stands were used and they recorded a hotter maximum temperature than today’s equipment.
Over the course of a year this could mean an average of 1.4 degrees in Summer and 0.2 degrees in Winter. But that’s an average, on a daily basis the difference would be even greater, thus “record maximums” on Greenwich or Glaisher stands are not directly comparable to those of Stevenson stands.
I imagine Nova would turn purple (the BOMs new shade for temps over 50) if we suggested installing the old Glaisher stands again and have average summertime temps jump upwards by a degree.
Heatwave in 1828, etc.
Nova makes reference to another of her posts which talks about Charles Sturt’s temperature recordings and a number of other.
No, they weren’t done using a Stevenson Screen either. Instead, according to Nova, he used a brewers thermometer and no this wasn’t shielded from the radiated heat in the way a Stevenson Screen does. In other words, Sturt thermometer records the temperature of the air AND the heat of any nearby objects, including the ground.
A true skeptic, one must wonder, did Sturt just fluke upon being in many places at just the right moment to capture a new record maximum, in some cases by more than 6° C? Or was his equipment and method of recording temperature different and biased high compared to modern equipment?
Nova unskeptically accepts older data whilst casting the usual merchant of doubt over current readings.
The BOM’s raw data adjustments have increased the warming trends in the raw data by around 40%.
As pointed out before, faulty amateur analysis made wrong conclusions which Nova unskeptically swallows.
Urban Heat Island Effect
Also strangely, the BOM seems to have no problems with the many temperature stations which are sited in areas where there has been substantial urban and industrial growth which will impact more recent warming due to the Urban Heat Island Effect.
We recently covered this myth too.
Nova casts doubt on modern records whilst unsketically placeing faith in unconfirmed, unsubstantiated older temperatures records recorded using non-standard equipment and by methods that don’t measure the same thing as modern equipment.
But does it matter anyway? Does this heatwave prove or disprove global warming? As IPCC head Pachauri said …
”It [last week's record temperatures] could be [a result of climate change], but I wouldn’t draw any conclusions on one single event. I think you have to take the whole aggregation over a period of time and then come up with the conclusion; which is precisely what we have done,” he said.
”They [the findings] are very very clear. Heatwaves are on the increase, extreme precipitation events are on the increase, and on that there is really no room for doubt any more,” he said.
And the science is there to back his statement … Increasing frequency, intensity and duration of observed global heatwaves and warm spells
By contrast, Nova has nothing but the usual “merchant of doubt” message based upon anecdotal evidence.