New paper finds that aging weather stations record much higher daytime temperatures, 1.63°C higher than new stations
While we are all watching the heat wave developing in the US southwest, here is something to consider. Albedo on the surfaces of weather station shelters changes with time, something I and the volunteers have documented with the Surface Stations project. For example, here’s a aged weather station where the whitewash coating is coming off and the bare wood is becoming exposed:
Back in 2007, Pat Michaels wrote in an American Spectator column “Not so Hot“:
“Weather equipment is very high-maintenance. The standard temperature shelter is painted white. If the paint wears or discolors, the shelter absorbs more of the sun’s heat and the thermometer inside will read artificially high. But keeping temperature stations well painted probably isn’t the highest priority in a poor country.”
Now there is proof that changes in station shield surfaces affect temperature
A paper published in the International Journal of Climatology finds that aging of the solar radiation screens on weather stations is causing a large positive bias in measured temperatures of 1.63°C, which by way of comparison is more than twice the global warming of 0.7°C recorded since the end of the Little Ice Age in 1850.
According to the authors, “During the comparison [of the new vs. 5 year old] and 1 to 3-year-old screens, significant temperature differences were recorded at different times of the day. The differences, wider than the uncertainty amplitude, demonstrate a systematic effect. The temperature measured with the older screen is larger, and the maximum instantaneous difference was 1.63 °C (for 0–5 years comparison) in daytime hours.
During night-time the two AWS’s measure the same temperature (within the uncertainty amplitude). This behaviour, increasing with increasing solar radiation intensity and decreasing with increasing wind speed, is attributed to a radiative heating effect. The screen ageing has compromised the shield effectiveness introducing a significant change in the temperature evaluation.” The paper is yet another blow to the unreliable, biased, and highly upward-adjusted temperature record.
The paper: http://onlinelibrary.wiley.com/doi/10.1002/joc.3765/abstract
Comparative analysis of the influence of solar radiation screen aging on temperature measurements by means of weather stations DOI: 10.1002/joc.3765
G. Lopardo et al
Abstract:
Solar radiation screens play a key role in automatic weather stations (AWS) performances. In this work, screen ageing effects on temperature measurements are examined. Paired temperature observations, traceable to national standards and with a well-defined uncertainty budget, were performed employing two naturally ventilated weather stations equipped with identical sensors and different only for their working time. Three different tests were carried out employing different aged AWSs: a 5-year-old AWS (AWS5) was compared with a new device (AWS0), a 1 year old (AWS1) was compared with both a 3 years old (AWS3) and a new one devices (AWS00). Due to solar and weather conditions exposure a degradation of the screen reflective coating is evident for the older AWSs (5 and 3 years old) and so a qualitative estimation of how different conditions of ageing affect the temperature drift was done.
During the comparison 0 to 5 and 1 to 3-year-old screens, significant temperature differences were recorded at different times of the day. The differences, wider than the uncertainty amplitude, demonstrate a systematic effect. The temperature measured with the older screen is larger, and the maximum instantaneous difference was 1.63 °C (for 0–5 years comparison) in daytime hours. During night-time the two AWS’s measure the same temperature (within the uncertainty amplitude). This behaviour, increasing with increasing solar radiation intensity and decreasing with increasing wind speed, is attributed to a radiative heating effect. The screen ageing has compromised the shield effectiveness introducing a significant change in the temperature evaluation.
The experimental results of a further comparison, between 0- and 1-year-old screens, confirm the same conclusion showing a negligible ageing effect, within the uncertainty amplitude.
h/t to The Hockey Schtick
Here’s the problem–because the Stevenson Screen stations were measuring lower than the MMTS stations that replaced them, the record-keepers decided that the MMTS stations had a cool bias, and should be adjusted upward. Removal of that upward adjustment would cut the rise in recent decades by maybe one-third, per my SWAG.
All data are good as long as they are homogeneous. The disasterous shift from CRS to MMTS shelters by NOAA in the mid 80’s destroyed the U.S. Climate Observing Network’s homogeneity.
Scott says (June 29, 2013 at 9:33 pm) Any idea whether the current algorithm considers the difference in max & min behavior as the paragraph I quote from you suggest should be possible to do?
There was a very useful discussion at Lucia’s and links to Zeke’s the latest NCDC paper at Lucia’s: http://rankexploits.com/musings/2013/uhi-paper-finally-published-in-jgr/
Errors made by correcting breakpoints caused by gradual deterioration of observation conditions and maintenance is discussed here: http://rankexploits.com/musings/2013/uhi-paper-finally-published-in-jgr/#comment-110147
have you ever a seen a simple experiment?…gathering several thermometers in a few square meters and monitoring temperature…
i repeat t a themometer mesasures its own temperature, the rest is assumption..i assume a themal equilibrium i assume, the box isn’t warmer and radiate .i assume the air outside the box is a the same temperature ; or is well mixed and so on…and you know that each one is false… but well we need to measure something don’t we?
Gail Combs says: ”
Peter Miller says:
June 29, 2013 at 3:33 pm
…..Can’t they make these weather stations out of white, UV resistant plastic? To be still using wood for these shelters seems almost archaic…
1. Plastic degrades too, especially white plastic. (Black has the best UV stability)
2. Historic screens are wood that is white washed. Any change, even a change in the type of paint will change the readings. We have seen enough manipulation of the raw data as it is without introducing another factor that can be used for fudging the data. …”
We should also note that the maximum typical UPVC rated lifetime is around 25 years, while wood can happily last for several hundred. More importantly, that UPVC lifetime is a period to failure – colour degradation (thereby altering the temperature) will start within a very few years. And it will be variable, depending on how much sun an individual installation has.
Plastic would be a VERY bad idea….