Are the Scripps calibration standards supposed to be world wide gold calibration standards used by everybody doing climate change work? Or are they for U.S. researchers? In other words does Europe have a gold standard calibration set or are we relying only on 1 measurement center on which we base all our measurements? If that is the case, then all the previous CO2 measurements need to be redone. How many papers using the faulty calibrations will be revised and republished? How many key fiundings, long accepted by the climate change establishment will be significantly questioned. On that, I won't hold my breath what knowning the politics of climate research today.
The magnitude of the recalibration is relatively small 0.16 ppmvAs.
It is the fact that
"....there has been no drift of the mole fraction, cannot be rejected for any of the Primaries with the statistics we have.Therefore, we assume that,there has been no drift until now...... The above does not imply that the defined WMOScale has not drifted".
They are talking about an unknown amount of "drift" possibly (probably?) over and above the amount they have recalibrated for.
Their own page (extracts shown as follows) on preparation and stability is littered with examples of drift potential, and those are only the ones they know about now. What others remain as yet undetected?
The manufacturing target of the CO2 test canisters is "within 5 umol/mol for near ambient concentrations." But this appears to be greater than the annual measured change of 1.3 ppmv.
"The zero air from both trapping agents was tested and found to be less than 5 umol/mol for CO2."
"Aquasorb is phosphorus pentoxide (P2O5). However, CO2 was found to increase by 2-5 umol/mol with this new drying material. This problem and the safety issue of cycling phosphoric acid in a high pressure system prompted the decision to discontinue use."
"The steel cylinders used in the past exhibited too much drift in CO2 mixing ratios, with half of these drifts on the order of 0.05 umol/mol CO2 per year [Komhyr, 1985] could be at different rates or of a different sign in each cylinder."
"There are some cases (8%) with evidence of drift greater than 0.045 umol/mol per year. For this reason, it is recommend that standards be recalibrated during long use and at the end of their useful volume. The drifts, as shown in the histogram, cannot be predicted. Drift in most of our standards is often undetectable for histories of less than 2.5 years. In some documented cases the drift was attributed to H2O mixing ratios greater than 5 umoles mole-1, stainless steel valves, or valves with packing materials, which preferentially absorb trace gases. There may be an increasing trend in the CO2 with decreasing cylinder pressure below 20 atmospheres. This is different in each cylinder or may not be present at all."
"There have been some cases of major drift (0.05 per mil 13C per week) of the CO2 stable isotopes, attributed to the Teflon paste used as the cylinder valve sealant and also to unknown regulator contamination. There may be some evidence for long-term drift of CO in aluminum cylinders as exhibited in smaller high-pressure cylinders [Paul Novelli, CMDL, personal communication, 1999]. This drift, however, is on the order of the measurement precision and has not yet been well quantified."
"Drifts have persisted for months due too evacuating the cylinder down to vacuum before filling. Drifts due to spiking, discussed below, have been eliminated by filling the cylinder immediately after spiking and filling the cylinder laid down. There is no evidence to show drifting due to the filling process described below. As a result of these experiences and to remain conservative about long-term unknown effects, the following steps have been adopted by CCGG..."
"The zero air is created with specific chemical traps for each trace gas. Carbon dioxide can be removed with sodium hydroxide, Ascarite (Thomas). Carbon monoxide is removed with Schutze reagent. The zero air from both trapping agents was tested and found to be less than 5 umol/mol for CO2.."
"Occasionally the targeted concentration is missed by an amount that requires adjustment. If the concentration of the standard is closer to ambient than the target concentration, it is easiest to blow this off and start over. Experimenting with introducing small volumes of high pressure (high or low concentrations) into the air stream have proven very time consuming due to the time necessary for the cylinder to become evenly mixed before obtaining a usable measurement from the standard."
"There is evidence that as the volume of pressurized air is used up, the trace gas can come off the walls in disproportionate amounts. This has sometimes been seen in cylinders with CO2 when a standard is used at pressures below 20 atm. Thus CO2 mole fraction may increase with pressure loss. This effect is variable and may not be measurable in all tanks."
NOAA Technical Memorandum ERL-14
CMDL/CARBON CYCLE GREENHOUSE GASES GROUP STANDARDS
PREPARATION AND STABILITY
Duane Kitzis
Conglong Zhao
http://www.cmdl.noaa.gov/ccgg/refgases/stdgases.html
Remember they are claiming to show accurately changes of 1.5ppmv over a year.
If they have made a mistake, or there is drift in the primary calibration, then all the figures produce by this method may be wrong.
Science should be about independent testing and replication, but if all the testers are using the same equipment, using the same calibration of the primary, then there is in fact no independent verification of the method or the calibration.
See also http://www.cmdl.noaa.gov/ccgg/refgases/reg.guide.html Guidelines For Standard Gas Cylinder and Pressure Regulator Use, for how complicated all this is to work in practice.
As far as I know in the early years SCRIPPS and now NOAA/ESRL's Global Monitoring Division (formerly CMDL) of the National Oceanic and Atmospheric Administration are the only source for the testing calibration gases and the equipment and methodology. I don't know whether the Europeans or others have their own methods, but I've never seen any data from them.
Their page showing possible additonal source of error is:
http://www.cmdl.noaa.gov/ccgg/refgases/airstandard.html
And their guidelines for use are here:
http://www.cmdl.noaa.gov/ccgg/refgases/reg.guide.html