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Shrinking Stevenson Screens cause global warming (and peeling paint, long grass…)

The Australian BOM has lost its way

Australia’s Bureau of Meteorology is paid more than a million dollars a day, and the planet is under seige, yet the paint is peeling off some Australian thermometer screens, the grass is long, and wasps are nesting in them. What once were large 230 litre wooden boxes have shrunk to 60 litres and are now even turning to plastic.  The old glass thermometers are being replaced with electronic gear that can record a burst of hot air — yet somehow those freak high spikes are supposed to be comparable to temperatures recorded 100 years ago by slow glass thermometers.

Old larger boxes protected thermometers from sudden changes in air temperature.

Stevenson Screens, Australia, Bureau of Meteorology.

Left: Len Walker with a 230L screen in 1940. Right: Blair Trewin with a modern 60L Stevenson screen.

Possibly the hardest thing to explain is that even though the BOM collected comparison data on the different types of thermometers, which might help to assess new versus old, they routinely throw the data away. Compounding that, the metadata on sites is incomplete, missing, lacking in documentation.  Giant six lane highways are built next to equipment sites but not recorded. There is a huge disconnect between the urgency and the fear of climate change and the care and attention paid to measuring the climate. Despite all this the BOM repeatedly tells the public that the science is settled, and we’re hitting new record temperatures which are supposedly accurate to a tenth of a degree.

Bill Johnston is a seasoned weather observer and agricultural climatologist.  He’s been documenting the dismal state of our national climate monitoring network for years, all unpaid. See his previous posts here on Bourke, Port Hedland, Canberra, and Sydney Observatory.

Bill Johnston’s paper: Blowing the whistle on Stevenson screens

Bring on an audit! — Jo


Australia’s climate-trust catastrophe!

A climate critique by Dr. Bill Johnston

The Bureau of Meteorology has lost its way. Replacement of standard 230-litre Stevenson screens with 60-litre ones, which accelerated over recent decades; automatic weather stations (AWS) becoming primary instruments in September 1996; installing PVC screens in the hottest places they could find, closing offices, sacking staff and reducing maintenance to one or fewer site-visits per year have warmed Australia’s climate.

Lack of site control is endemic and it’s not true that changes in data are due to climate change and warming. Small Stevenson screens relocated to dusty paddocks and airports, which are seldom cleaned or repainted, are invariably biased-high (Figure 1). It matters that paint peels off and screens lose their lustre, grime builds up and that grass is not regularly mowed (Figure 2). Recent record temperatures and increases in the frequency of warm days are predominantly due to relocating screens to warmer aspects, AWS and small screens becoming primary instruments, and lack of maintenance.

Stevenson Screens, Australian, Bureau of Meteorology.

Figure 1. While the screen and other equipment at Wagga Wagga airport were well maintained by Bureau staff in June 2016 (left), placement of the AWS temperature probes 2-cm closer to the north-facing rear of the screen made the temperature warmer on warm days. At Rutherglen (right), by July 2019, the neglected screen was grimy; home to a mud wasp (arrowed) and outside paint was peeling around the roof and louvers. Lack of regular maintenance results in bias and causes the frequency of warm days to increase. (Sensors measure relative humidity (RH) and temperature (T).). Stevenson Screens, Australian, Bureau of Meteorology.


The Bureau has lost its way

Standards have slipped and the Bureau’s core function of monitoring the weather can no longer be trusted. The community is poorly served by its penchant for hitting the headlines with exaggerated claims of record hot days, months and years in time for the evening news.

Even worse, in 2017 they established seven new sites in southwestern NSW in the warmest places they could find using PVC screens with mat-black interiors that radiate heat onto the instruments on warm days. It is therefore no coincidence that temperatures have increased in recent time; that records are regularly smashed and that heatwaves and extremes seem more frequent. However, it’s a major problem for climate catastrophists that trends and changes don’t reflect what’s actually happening with the weather.

The climate emergency doesn’t exist. In order to fit the narrative, Australia’s Bureau of Meteorology has altered the conditions under which temperature is measured. Aided by the Monash misinformation hub, the ABC, The Conversation the Fairfax press and The Guardian, a campaign is underway to tag our normal weather as non-normal and extreme.

Australian BOM

Figure 2. Deterioration of the roof and north-facing rear of the Rutherglen screen in July 2019 caused by poor maintenance is likely to result in bias on warm days (Left). On the right is the overgrown automatic weather station at Bridgetown (WA) in September 2015. (Photographs by the Author.).

 Bill Johnston’s paper: Blowing the whistle on Stevenson screens

 Past Posts:

All Bill Johnston’s posts: http://joannenova.com.au/tag/johnston-bill/

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