Back in 2007, climate ground station researcher, Anthony Watts came to the attention of the world’s climate scientists afer he surveyed over 75% of the 1200-plus U.S weather stations and found many to be inaccurate by more than 2°C, largely due to being located within 10 meters of an artificial heating source. But another little-reported fact that Watts uncovered was that modern paints now applied to the temperature measuring boxes (called Stevenson screens) are also seriously contaminating the measurements of global ground temperature stations.
Watts said, “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.”
Watts has discovered that the modern paints absorb far higher levels of solar radiation than the old-fashioned whitewash traditionally used on these stations ( see image below). The newer paints cause greater absorption of heat unlike the old-fashioned whitewashed variety, thus increasingly contaminating the temperature data.
So how does the temperature contamination effect of paint work? 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 readings. This is something easily overlooked by the casual observer because it isn’t only the energy from the sun we see in the visible spectrum that creates a heating effect on Earth, the invisible part of the light spectrum also plays a major role in warming our planet.
Anthony Watts explains why this issue is set to become the next big climate issue:
Bad Paint Job = Rising Surface Temperatures
“In a nutshell, nobody seems to have experimentally investigated this issue. 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.”