Many of you may recall that I got my start in climate skepticism back in 2006 when I started looking at the paint on Stevenson Screens – because there was a change from the original lime-whitewash paint in the 1890s to modern latex paint. I figured there was a bias, and latex paint made the shelter warmer due its different IR signature. Temperature sensor tests over a month proved I was right. But in looking at temperature shelters in my area, I discovered an even bigger problem – most were sited near heat sources and heat sinks, in contradiction to NOAA’s own published siting standards. This started my journey to uncover just how bad the temperature observing network actually was. Comprehensive reports I made in 2009 and again in 2022 showed that surface measurements were a huge warm biased mess. This paper is over 10 years old, but I somehow missed it. I’m correcting that oversight.
Now, to add to that mess, comes this revelation – the Australian Bureau of Meteorology changed the size of Stevenson Screens to something that had just ~ 25% of the volume of the original, and did not run parallel tests to see if the conversion mattered. – Anthony
Craig Kelly of the AFEE in Australia writes on X.com
The peer-reviewed science confirms that shrinking the size of Stevenson Screens increased average temperatures across a year by 0.54°C and, on hot summer days, it can increase the maximum temperature by 1.7°C. https://waclimate.net/stevenson-sizes.pdf Yet the BOM denies the existence of this peer-reviewed science, pretends that it doesn’t exist, and claims that shrinking the screens by 74% had no effect on the recorded temperatures.
Furthermore, at every weather station where the BOM replaced the traditional “large” Stevenson Screens with smaller ones, they ripped out the large ones and replaced them with the small ones on the very same day. This is contrary to long-established practices, which require that when you change measuring equipment, you keep parallel data from both setups to determine whether the equipment change may have introduced a warming or cooling bias into the record.
If you wanted to artificially inflate temperatures and create new “record hot days” to generate propaganda for the climate cult, you’d do exactly what the BOM did: shrink the size of the Stevenson Screens. And if you wanted to cover up your malfeasance and fraud, you’d rip out the large screens and replace them with the small ones on the very same day so there would be no parallel data — exactly what the BOM did.
Attached is a photograph from the Sydney Observatory from 1947 showing the thermometers that officially recorded Sydney’s temperatures housed inside a traditional ‘large’ Stevenson Screen – with an internal volume of approximately 0.23m3. The BOM has shrunk the size of the Stevenson Screens, reducing the internal volume to just 0.06m3 – a 74% reduction. By shrinking the Stevenson Screens in such a manner, how much hotter will the recorded temperatures be inside the smaller screen on a hot and windless day?
Figure 1. Internal view of the large Stevenson screen at Sydney Observatory in 1947 (Top above, black and white image) and the small screen at Wagga Wagga airport in June 2016 (lower above, colour image). While thermometers in the 230-litre screen are exposed on the same plane, the electronic probe at Wagga Wagga is placed behind the frame about 2 cm closer to the rear of the screen, which faces north to the sun. According to metadata, the 60-litre screen at Wagga Wagga was installed on 10 January 2001 and although thermometers were removed on 28 April 2016 inter-comparative data is unavailable. Source: BoMWatch.
From the paper:
The main findings of this research are summarized as follows:
- An overheating of air temperature inside the medium-sized Stevenson screen was detected in comparison to the large-sized Stevenson screen throughout the year. This bias affected daily maximum air temperature records, especially during the warm season (May to October) and at 1300 UTC.
- The weather conditions enhancing this overheating bias (not statistically significant) are associated with clear skies, high solar radiation rates, weak winds and low relative humidity values.
- Comparison to nearby station have revealed that the different size of the naturally ventilated wooden Stevenson screens have an impact on mean, maximum and daily air temperature range. These kinds of investigations are crucial for removing inhomogeneities and accurately assessing the
spatio-temporal variability and long-term trends of near-surface air temperature measurements.
