But the BoM fails to say that outside the Hobart urban heat island (UHI) record warmth is harder to find.
I checked the following stations around the Hobart region – first the mean monthly max – only Tasman Island agreed with Hobart but the site has only operated from 2002.
then the mean monthly min gives a similar result.
So the BoM should have told the ABC that although central Hobart had a record warm October – few other sites in the district confirmed that so on balance you would assume that the UHI effect has been quietly ramping up warmth in Hobart data for a ~century.
Quite so. Instead of using the data to educate the public about the urban heat island effect, they trumpet the record without explanation so as to reinforce the global warming myth.
Mt Wellington is only about 10 kms west of downtown Hobart, but high enough and windy enough not to be affected much by Hobart’s UHI. It missed the record by a whopping 1.4 degrees. Even the airport, on the other side of town, and itself subject to UHI both from its own redevelopment and urbanisation around it, only equalled its previous high.
In decades past, the BoM might have thought it was part of its responsibility to explain the data properly instead of leaving out what one needs to know to understand them.
To see the cause of UHI in this case, check the time-lapse satellite pictures (earthengine.google.com/timelapse/) of the development of the Hobart area over recent decades.
Looking at it again I am not so sure about the UHI, since all three places – Hobart, the airport and Mt Wellington, had their highest previous October mean maximum in 2015. Yet only two years later there is a 1.7 degree difference in the anomalies between Hobart and Mt Wellington. Not impossible I suppose but a somewhat remarkable result. Cloud every day on the mountain but not in town? Who knows?
Meanwhile I notice that every single day’s reading for Hobart in October is still in italics on the BoM’s site here: www.bom.gov.au/jsp/ncc/cdio/weatherData/av?p_nccObsCode=122&p_display_type=dailyDataFile&p_startYear=&p_c=&p_stn_num=094029, with the explanation that “Data within the table which are in italics represent observations which have not been fully quality controlled, a process which may take a number of months to complete. While these data may be correct, you should exercise caution in their use.” Doesn’t seem like they are using too much caution themselves, rushing into print with their “highest ever” story…
The location of Hobart with the high relief, river, coastal setting – all factors that will perturb, modify, blur and UHI effects. But it is certain that the physical laws operate re concrete and tarmac retaining daytime heat to release at night. Also the release of heat due to winter heating of buildings, vehicles etc. Over time the UHI does show in data.