Another Temperature Bias: The Shrinking Stevenson Screen = Warming

by A. Watts, Feb 8, 2026 in WUWT


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