Let’s play the Heatwaves PR game. If CO2 had an effect we’d see a significant increase in the rate of global warming over the decades since WWII, the models would work, and climate scientists would be able to predict our climate. Since none of that is true, those with a political agenda have to clutch at noisy but marketable extremes instead. Apparently even a half-true, noisy, non-causal link is good enough for post-modern scientists.
Heatwaves are perfect for generating scientific sounding fear, but not so useful for generating actual scientific knowledge. There are an infinity of ways to measure them. They can last 3 days – 160 days, and be cut off at any number from 35 – 40C, or at some percentile outlier. They can be measured one town at a time, or on a regional or state-wide level. The permutations are rich with headline scoring possibilities. And in the end, on a long warming trend that started 300 years ago, it is obvious, inevitable, and predictable that we should score more now. What’s surprising is how often we don’t.
On ABC radio before Easter, Dr Vertessy, Director and CEO of the Bureau of Meteorology, claimed that we are seeing “of the order of five times the number of very serious heatwaves” as in the middle of last century [listen at 11 mins]. Ken Stewart wrote to Vertussy and asked what metrics he used to define heatwaves. Nearly two weeks later, Vertussy has not replied, so Ken analyzed the records himself using a 40C cut off, and also looking for the top 5% of summer maximums.
The end result is that it can be said that there happens to be more heatwaves in Adelaide, but there are less heatwaves in Sydney, Melbourne, Hobart, or Darwin. When will the BOM issue headlines declaring that for nearly nine million Australians in Hobart, Melbourne, Darwin and Sydney there are less heatwaves now than there used to be. Aren’t CO2 emissions useful?
It goes without saying (nearly) that there is older Stevenson screen data for most of these locations which isn’t included, though I “can’t think why” this important historic data would be ignored.
Melbourne — top 5% “hot scoring” days (Click to enlarge)
Melbourne — days over 40C
Sydney –days over 40C
Sydney – top 5% “hot scoring” days
Hobart — days over 40C
Darwin — top 5% “hot scoring” days
I’ve included Perth to show how useful heatwaves are to generate any headline you want.
Perth — top 5% “hot scoring” days
Perth — days over 40C
As Chris Gillham notes in an email, the Perth ACORN data comes from two stations — the airport and the inner city. But the airport’s long-term maximum is 1.2C warmer than the city, because it’s about 10 km further inland from the coast. If Guildford is used, which is closer, the warming trend would be much less.
“A far more suitable matching station for ACORN Perth Airport is Guildford Post Office, which took temps about two km due north of the current airport screen from 1901 to 1954 but which only provides monthlies and not dailies. The BoM almost certainly has the daily observation sheets and their reluctance to digitise might be due to Guildford PO 1901-1954 having a mean max of 24.8C compared to Perth Airport’s 1945-2014 mean max of 24.5C (2000-14 25.3C) and Perth RO 1897-1991 at 23.3C. The RO comparison achieves a 2C raw max increase to 2000-14 whereas the much closer neighbouring Guildford PO only warmed by 0.5C. It’s also worth noting that in the raw overlap years from June 1944 to April 1992, Perth Regional Office had 110 days at or above 40C, while Perth Airport had 175 days at or above 40C. It’s naturally hotter inland with more heatwave days.”
The end result is that politically correct scientists can find any headline they want using the Heatwave Randomiser.TM. Scientifically correct scientists would never cherry pick an irrelevant, unreliable, non-indicator. A half-truth is not The Truth.
The ABC interviewer, Richard Aedy, allows Vertessy to use blanket motherhood statements without any specific details in support against the articles in The Australian last year [at 12-15 minutes]. He’s feeding “Dorothy Dixer” questions to allow Vertessy to appear to reply, but it’s more an advertorial than an interview. Aedy has made no effort to research the questions raised in those articles. Thus a government funded public broadcaster interviews government funded public servant to produce propaganda about the success of government funding, with the prospect of a global agreement to build a bigger and less accountable layer of government in Paris later this year. The message between the lines from both is “vote for big-governments.”
Ken’s full post has graphs for other capitals.