|Stevenson Screen at the NWS office in Monterey –
good paint but right next to asphalt parking lot and concrete walk –
a definite no-no!
After reading an excellent paper about the biases that have crept in to temperature measurements world wide titled: Unresolved Issues with the Assessment of Multi-Decadal Global Land-Surface Temperature Trends I decided to contact the main researcher.
Today I had an extraordinary exchange with the senior climate research scientist, Roger Pielke Sr. from the University of Colorado. In this exchange, he expressed interest in some observations I’ve made about the state of temperature measurements used to create the climatic record set used in climate modeling. You can see the exchange here.
In a nutshell, nobody seems to have experimentally investigated this issue I raised. Last year I posted an essay on the subject of paint and weather stations shelters at http://www.globalwarmingindex.com but the idea I’ve had goes back to the early 1990’s, and I haven’t experimentally investigated it either. It seems that weather stations shelters known as Stevenson Screens (the white chicken coop like boxes on stilts housing thermometers outdoors) were originally painted with whitewash, which is a lime based paint, and reflective of infra-red radiation, but its no longer available, and newer paints have been used that much different IR characteristics.
Why is this important? Well, paints that appear "white" and reflective in visible light have different properties in infrared. Some paints can even appear nearly "black" and absorb a LOT of infrared, and thus biases the thermometer. So the repainting of thousands of Stevenson screens worldwide with paints of uncertain infrared characteristics was another bias that has crept into the instrumental temperature records. Read here a report from the Arizona State University department of Physics and Astronomy of the response of paint pigments to infrared:
Almost all the paint pigments have the same properties as Si and Gallium Arsenide. They are transparent to infrared light. This transparency to IR occurs because the paint pigments are nearly all oxides (such as titanium white, titanium oxide) or sulfides (such as the red vermilion, mercury sulfide). In pure form, they are insulators or semiconductors with almost no electrons available for light absorption in the IR. – Arizona State University read more
Infrared spectral analysis of CaCO3, Calcium Carbonate, the main component of whitewash paint
This means that the infrared radiated from the sun, ground, and nearby objects goes straight to the wood, heating it, and likley biases the thermometer inside the shelter. Whitewash was specifically chosen to paint the Stevenson Screens because it it had some reflective infra-red properties (note graph above). Yet you don’t read anything about this on repainting of weather shelters worldwide because there’s no maintenance record to correlate the painting, its been done "ad hoc" by local operators of the stations. So some researchers just shrug their shoulders and use the data anyway. And when those same researchers are looking for "warming signatures", often measured in tenths of degrees, I have reason to doubt the findings knowing the possibility that significant measurement bias that has crept in.
Coupled with other documented biases, it is becoming clearer that the data collection methods used to get surface temperatures may be riddled with biases and errors.
Well. its go time. I’m going to conduct an experiment, of all things, on paints, wood, and thermometer bias. I’ll be setting up controls, measurement practices, calibrations, and real-time data recording. It will be live on the Internet too as we watch different combinations of materials and how they react. And, I’m going to be visiting every weather station I can in California. My foray into climate modeling practice will have to wait, because if the data is biased or faulty, climate modeling then becomes nothing more than garbage in, garbage out.