Lon Glazner, a fellow blogger and local electronics engineer made some comments about my post on the NASA/CSU study on California temperatures. Well that got me started…so below are Lon’s comments and my reply along with a fun technical challenge. For those of you that read this blog, but disagree with my views, I invite you to read this carefully.
Anthony,
You make a number of good points. Particularly in the fact that the writers may have applied changes in urban temperature measurements over large regions for graphical impact.
As someone who has designed and built electronic temperature sensors I have certain concerns about the data itself.
Unless temperature sensors are regularly calibrated I think it is unreasonable to expect accuracy of greater than a couple of degrees.
Even some that are calibrated may not have good accuracy. The LM34 which is a commonly used semiconductor for measuring temperature is +/-2 degrees F. This is pretty typical of analog or digital semconductor sensors. The temperature error for this part is also non-linear, and so it’s not a simple offset that you have to account for during data collection. Furthermore, there are lots of additional errors that can creep into a temperature measuring device beyond the sensor itself.
http://www.national.com/pf/LM/LM34.html
One could argue that numerical analysis done on data points would tease out errors. But if a scientist doesn’t know the exact accuracy of a temperature sensor then they couldn’t account for errors in their system.
Some of the temperature sensing stations may be very accurate and regularly calibrated. But maybe they’re not?
I have a hard time trusting that the data is accurate to the level of identifying 1 or 2 degree changes over decades. This is especially true since the techniques of making these measurements have changes over that time frame.
Lon
Lon, thank you for the comments. FINALLY somebody who understands the kind of biases that creep into temperature measurements!
I’m innately familiar with National Semi’s LM34 and it’s accuracy problems. One of my early jobs at my university as a research assistant was to create remote electronic weather stations. I soon learned how inaccurate many electronic devices can be in temperature measurement.
The problem with the National Weather Service temperature data sets (and world data sets too) is that they are full of biases and errors that I’m not sure have been accurately accounted for. People such as Jim Price, from CSUC who is on the IPCC say they have been, yet nobody has shown me any hard evidence of such. I’d be a lot less skeptical if I could see how the IPCC accounted for temperature measurement biases. But they won’t share.
Some people that I try to explain this to accuse me of splitting hairs. But these bias problems in temperature measurement are quite real.
What works against my arguments about the difficulty in getting accurate temperature records is the everyday simplicity of temperature and its common measurement. We live by temperature, we have it reported constantly, we all have thermometers at home, we measure our childrens fevers with thermometers, we barbeque with thermometers.
Measuring temperature is easy right? You just stick the thermometer in whatever gas, liquid, or solid you want to measure the temperature of and voila’ there it is. People tend to think of thermometers as perfect devices. Some very expensive calibrated thermometers, are close to perfect, especially when taking measurements in a closed system, like a fermenatation vat at Sierra Nevada.
But in an open system in our atmosphere, there are many many more biases that can affect the measurement within a few inches or feet of the thermometer. Here’s just a few:
– Reflected sunlight from nearby building or objects
– Re-radiated infrared from nearby cement or asphalt surfaces or the ground itself (which is why airports make terrible places for temperature measurement)
– The structure that the thermometer is mounted to, can conduct heat to the thermometer
Now add to that:
– Accuracy of the thermometer itself
– Linearity of the thermometer over its measurement range
– Long term repeatability of the thermometer’s accuracy
– Long term repeatability of the thermometer’s linearity
And then we have urban effects such as:
– Localized vegetatation removal or addition over time
– Localized building changes over time
– Localized asphalt or concrete surfaces addition or removal
And finally within the global temperature records data set we find instances of:
– Changing the location of the weather station and/or its thermometer
– Changing the thermometer itself at some point – i.e. repair/replace
– Changing the thermometer type, from mercury, to electronic (thats been done at thousands of weather stations worldwide)
– Variations in temperature measurement devices from country to country, even though the World Meteorological Organization has specifications, they are not always followed.
– Changes in thermometer shelter, different types of paint over time, all which have different absorptive and reflective properties.
– Changes in the observer recording the temperature, some may round up, others round down numbers. BTW for about 75 years, all temperature records were manually recorded.
Ok with all these biases and possible errors that you have to account for to make long term temperature measurement reflect the true temperature of the location, can you be absolutely sure of the data integrity? Especially when you are looking for trends that may be 1 degree or less over 50-100 years? I can tell you that I’ve looked at these climatological data sets, and NONE of them come with a calibration record for the thermometer, or even a description of the make/model used at that location. There are notations in the records that say things like “station relocated to accomodate construction” or “thermometer replaced” which can give clues to the data integrity possibly changing but the climate researcher is left to make a judgement call on the viability of the data without anything to gauge the sensor or its local environment.
Or lets try a thought experiment Lon, you’ve been commissioned by the IPCC to make a new thermometer for use around the world at climate measurement stations. As an electrical engineer, could you design an air temperature thermometer that is:
– Linear to within 0.1% over a temperature range of -20F to 120F
– Accurate to within 0.1 degree F over that same range
– Repeatable in linearity and accuracy defined above for a period of 20 years. Or even 10 years.
– Identical withing the specs above, so that if one fails, it can be immediately swapped with another one from parts stock with no worry about introducing bias
Ok there’s your challenge. Could you do it?
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I agree that measuring temperature is a tricky thing, and placing sensors near parking lots, a/c units, and other natural or man-made structures could lead to potential errors. Now we just need to tell the glaciers that the measurements were wrong so they can stop melting!
Just wanted to comment on the receding glacier issue. Two points: First, not all glaciers are receding and a good number of them are advancing. Second, glaciers have been receding overall world-wide since the end of the last ice age. That’s how it ended – the glaciers receded. When the majority of the glaciers start to advance is when we need to be concerned.
Anthony:
Three things, First, your link for weather station standards does not seem to be the right link. It is on a related topic, but says nothing about the 100′ rule, for example. My apologies if I missed something there.
Second, When doing station audits, I think there would be some value in getting a picture or assessment of the roof of the Stephenson shelter, where feasible (one can just hold a camera up there if it is above eye level). This is probably the hardest part to keep painted.
Three, I think that it would be a fair question to ask the supervisor of the station if it is ever in the shade. This might not matter for max/min temperatures but could be relevant for other averaging.
***REPLY FROM ANTHONY*** There is a link to a PDF document with specs on the NOAA page I reference about siting
You are doing a wonderful job!
Thank you for injecting a much-needed note of reality into green hysteria. Their desperation to manufacture a problem they can use to increase taxes and regulations is more blatantly obvious than ever. Thanks, again.
I live in Palm Desert CA and my temp readings match AccuWeather’s until temps reach above 100 then they post too high readings which increase even more as temp rises suggesting that thier observation sites may be impacted by re-radiated infrared. The sites are located in the middle of acres of asphalt runways at Palm Springs and Thermal Airports. Each City in the area is given a temperature based on historical data relative to the airports’ readings. Gee…do you think the posted temps may not accurately depict the actual temps, (unless you happen to live in the middle of the runways at the airports)?
I always thought it was the opposite.
Our weather stations may report a high in town of 92F but our thermometers out here in the country, near no asphalt or the like, read 102 to 105. It is horrifyingly hot to feel.
SO I figured the weather stations were just reporting the temps below what they really are to keep public panic down, as usual. Now you say it’s the opposite, it isn’t getting warmer on average?
I understand people will use global warming as an agenda to make money and gain power. This ticks me off, it’s taking the focus off of the real environmental issues at hand. All I hear now is a lot of hot air from both sides.
People like you will say it’s not getting warmer on average because your money is already tied up in the things that have screwed things up to begin with. Nice try. Both sides aggravate me.
I have to listen a geologist elder in my family yap on about the temps not really getting any warmer and how everything is fine, yada yada yada. Guess where his money is tied up? Coal, gas, mining, oil. Surprise surprise. *sigh*