thaumaturgy
Well-Known Member
Now, will you finally answer my question: Do you think the modern thermometers are worse than those used in 1900 and thus in need of more 'correction' than those of 1900?
No I do not. I suspect Phileas hit the nail on the head when he said we don't really know how much these measurements need to be corrected. But I don't know that for sure.
Remember a lot of chemistry, the fundamentals, were established by people with home-made temperature measurement devices.
No one will ever have perfection, but one needs verification. If a model can't model the present, why should I believe what it says about the future?
That's why I was so happy to see the article from the University of Utah which states that modern coupled models appear to accurately model current climate:
(emphasis added)."Coupled models are becoming increasingly reliable tools for understanding climate and climate change, and the best models are now capable of simulating present-day climate with accuracy approaching conventional atmospheric observations," said Thomas Reichler of Utahs Department of Meteorology. "We can now place a much higher level of confidence in model-based projections of climate change than in the past."
(SOURCE)
Now, I have addressed your issues but you have not ever addressed my question about the editorial warming. Do you think it OK for editing to add 0.3 deg C to the temperature of the US? Yes or no?
Do you mean in the same way I "edit" the voltage output of a pH meter to make it read the same pH for a standardized buffer each day despite the fact that the probe may be aging and changing and "shifting" it's slope?
Yeah, I'm quite ok with that.
Here's a brief look at my morning as I blatantly correct the output of analytical instruments in the service of science:
Each day I go into the lab and I need to measure the pH of solutions. Each morning I start out by calibrating the pH meter. It is an electrochemical cell that reads out a voltage depending on how much hydrogen ion is in the solution.
No pH meter made can just look at a solution and tell you how many moles of H[sup]+[/sup] ions are in there, but it can tell you all about the electrical features of that solution.
Each and every day it measures a given voltage. If I were to simply measure the voltage each day I would have a measure that, depending on conditions will only stand in as a proxy for the actual pH. The voltage could drift over time but it would still measure what it measures.
When I calibrate the pH probe (which should be done very regularly) what I am doing is telling the machine that under the present conditions, however the probe itself is working, this is the correlation between the voltage and the pH scale. I am inducing a correlation. I am telling it that no matter how it is functioning that day (and it might have developed some electrical offset or other problem) that I am going to arbitrarily define whatever the voltage difference seen for the different known pH solutions is how it will correlate for that day. Even though there is an ideal theoretical correlation that would, under perfect conditions, be exactly the same every day.
In essence I am correcting the data on a daily basis for any sort of changes in the pH probe. (Maintaining and Calibrating pH Electrodes / pH Probes)
Want proof that pH probes change over time? Then keep track of the slope calculated each day for several months. As a probe ages the slope becomes less accurate. After a certain point the slope calculated during the calibration phase is too far off from the theoretically idea slope to allow the data to be reliable anymore. But during that time, over time, the probe can be getting worse but still be used precisely because I am calibrating it.
In addition the pH measurement is compensated for temperature of the solution. Another correction. pH can change slightly with temperature due to the ionization reaction itself, but also because the pH probe itself is affected by temperature. Hence a temperature measurement should be included. (Temperature and pH Measurement </head>)
[FONT="] Since pH values are temperature dependent, pH applications require some form of temperature compensation to ensure standardizes pH values. Meters and controllers with automatic temperature compensation (ATC) receive a continuous signal from a temperature element and automatically correct the pH value based on the temperature of the solution.[/FONT]
(http://www.4oakton.com/TechTips/TT_ph.pdf)
To assume that each day the most reasonable activity would be to just measure the raw voltage and be done with it is to miss the point of even running the instrument. Data is processed, filtered, correlated with something and output. Without those corrections it would give me little more useful information than a random noise generator.
This has inspired me a bit. I think I'm going to go in tomorrow and run around the lab measuring the raw voltage (without any calibration) of a single buffer solution on all the different pH meters we have. If I think of it I'll post the values. It will be on the same solution so it should be a nice test. There's some old and crotchety pH probes. I rather suspect they will have different voltages, especially if they aren't calibrated. I look forward to this little experiment!
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