From the National Physical Laboratory, a rather curious press release that had a fact I didn’t know: the gas calibration standard sample for measuring CO2 comes from an obscure location in the Rocky Mountains. One would have thought Mauna Loa would be the source. I’ve added a Google Earth map below to show the location. The only problem I have is that with any synthetic standard used as a baseline, it can be subject to synthesis error.
NPL scientists blend synthetic air to measure climate change
New gas standard to meet increasing demand
Scientists at the National Physical Laboratory (NPL) have produced a synthetic air reference standard which can be used to accurately measure levels of carbon dioxide and methane in the atmosphere. This will greatly help scientists contribute to our understanding of climate change.
A paper published in Analytical Chemistry describes how researchers at NPL have created a synthetic gas standard for the first time, which is comparable to the World Meteorological Organisation (WMO) scale and can be quickly produced in a laboratory and distributed, meeting growing demand.
The bulk of demand for gas standards comes from atmospheric monitoring stations around the world. The data collected from these is important to our understanding of climate change.
To reliably compare the concentration of carbon dioxide and methane in air at different locations, and over time, a primary standard to which all measurements relate is required. We must be able to relate the measurements to a trusted base unit, so we can reliably compare measurement between London and Beijing, or between 1990 and 2014.
The current primary standards for carbon dioxide and methane are a suite of cylinders of compressed air captured from Niwot Ridge in Colorado and held at the National Oceanic and Atmospheric Administration (NOAA).
They are used to create secondary standards, which are used to calibrate the instruments that measure greenhouse gasses around the world.
A new improved measurement technique – cavity ring-down spectroscopy (CRDS) – has resulted in a dramatic increase in the number of atmospheric measurements taken. As the requirement for data that is comparable to the WMO scale increases, there is a corresponding increase in the demand for comparable reference standards.
Supplying the demand for reference standards comparable to the WMO scale is becoming an issue. An infrastructure to disseminate reference standards prepared gravimetrically – i.e. by weighing the gas in the cylinder – that are traceable to the International System of Units (SI) offers a means of broadening availability. These could overcome the cost and complexity of sampling air under global background conditions which can only be carried out at remote locations.
NPL has developed a solution, producing a synthetic standard which can be used to calibrate carbon dioxide and methane measuring instruments. Rather than sampling air directly, NPL created the sample in the laboratory by carefully blending a mix of gaseous components found in air.
However preparing reference standards synthetically presents a significant challenge. Industrially produced carbon dioxide has a different isotopic distribution to that of atmospheric air, which measurement instruments read differently.
Paul Brewer, Principal Research Scientist at NPL, said: “By using high accuracy gravimetry, we were able to prepare a gas mixture that accurately replicated the natural occurring isotopic carbon dioxide. The samples were tested using NPL’s world leading measurement equipment and expertise, which demonstrated that the synthetic standard was comparable with the NOAA standard and suitable for use with the international measurement scale for atmospheric monitoring.”
The research has demonstrated that air standards comparable to the WMO scale can be prepared synthetically with an isotopic distribution matching that in the atmosphere. The methods used can be replicated, leading to widespread availability of standards for globally monitoring these two high impact greenhouse gasses. For the international atmospheric monitoring community and for gas companies, this could solve the pressing supply issue.
The project has received widespread support from the atmospheric measurement community. Euan G. Nisbet, Foundation Professor of Earth Sciences at Royal Holloway maintains an Atlantic network of greenhouse gas measurements. He says: “Standards are a critical problem in greenhouse gas measurement. Developing high accuracy reference standards of carbon dioxide and methane with international comparability, and traceability to the SI, will greatly contribute to our work, and to improving our understanding of how greenhouse gases affect the atmosphere.”
The full paper can be viewed here: http://pubs.acs.org/doi/abs/10.1021/ac403982m
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for all those who want CO2 measured accurately – be careful what you wish for.
2011: Bloomberg: Earth Networks, Scripps to Deploy 100 Carbon Monitoring Stations Globally
Scientists and carbon traders typically rely on self- reported data from governments and businesses, based on consumption of fossil fuels, to determine how much a country or region is emitting.
“I don’t trust some governments to accurately measure their carbon inventories,” Scripps director Tony Haymet said in an interview. “We need these top-down measurements to verify.”…
On Jan. 10, there was a “fairly moderate” concentration of carbon dioxide in the air, he said yesterday. “Today, the wind has shifted to the south, and carbon measurements are significantly higher because of all the pollution coming from Baltimore.”
http://www.bloomberg.com/news/2011-01-12/earth-networks-scripps-to-deploy-100-carbon-monitoring-stations-globally.html
Jaakko Kateenkorva says:
February 27, 2014 at 2:03 pm
Makes me wonder what is the estimated uncertainty of the reference standard for the carbon dioxide and methane assays (measured in parts per million and parts per billion respectively).
Keeling senior made a glass instrument himself (he had good skills on glass blowing) in the 1950’s to calibrate any CO2 measurements/devices with a gravimetric method accurate to 1:40,000. Good enough to calibrate the standard NDIR measurements accurate to better than 0.1 ppmv. The above calibration instrument was in use at Scripps until a few years ago to prepare calibration gases for Scripps for samples taken at Mauna Loa, independent of NOAA, which did take over the calibrations from Scripps some decade ago. The NOAA (continuous) and Scripps (flask) measurements differ maximum 0.1 ppmv from each other (1 sigma), each with their own calibration gases and instruments.
The only problem they didn’t know at the beginning of the measurements was that their calibration gases were mixtures of nitrogen and CO2, not air and CO2, out of fear that inside oxydation of the containers might give a deteoration of the mixture. When years later was observed that the instruments did show different results with CO2 in N2 than with CO2 in air, they recalibrated all instruments and changed all previous values accordingly (the raw voltage data still were available).
I don’t know the accuracy of the CH4 standards…
kuhnkat says:
February 27, 2014 at 12:13 pm
But, but, but, Finaglebean has assured us there is no question of the reliability of the official monitoring networks output, yet, they didn’t even have a reliable standard to work against.
If they monitor your blood composition, you rely on good standards of today. That doesn’t mean that the old standards were bad, only that modern blood tests have a much better resolution, thus that the standards to compare with must be more accurate too…
pat says:
February 27, 2014 at 2:22 pm
for all those who want CO2 measured accurately – be careful what you wish for.
That story has nothing to do with accurate measurements of “background” CO2 levels. These are measured far away from the main industrial and natural sources and sinks: mid oceans or coastal and with wind from the seaside.
The 100 extra stations are tall towers to be installed (and partly already installed) over land to measure regional sources and sinks of CO2 and specifically where the human emissions originate. The latter nowadays are calculated from fossil fuel sales (taxes!), but probably underestimated due to under-the-counter sales…
The NBS used to be in Boulder. It is now NIST. They still do the same stuff. They are most famous for time and frequency standards. WWVB on 60 KHz and WWV at 5MHz, 10MHz, and 15MHz. For WWV you can set your watch by it if you can decode the 100 Hz subcarrier. WWVB does it by 17 dB power changes.
Industrial CO2 is produced from various processes, e.g. recovered from steam methane reforming, refining, recovered from fermentation, etc. Most industrial CO2 is recovered from gas wells. It is not practical to recover it directly from air.
Jeff an klem, CO2 isn’t only measured at Mauna Loa – it’s measured all over the globe. See here:
http://www.esrl.noaa.gov/gmd/dv/iadv/
Ferdinand Engelbeen –
have noted your comments, tho i was considering NPL’s own stated purposes at a link i provided earlier. appreciate u pointing out the difference in this thread’s particular case, tho.
Quantitative Uncertainty
Re: “it can be subject to synthesis error.”
Paul Brewer et al. establish an objective reproducible standard traceable to fundamental primary standards at national labs like NPL and NIST.
Ref: (18) International Organization for Standardization (ISO) <Guide to the Expression of Uncertainty in Measurement (GUM); Geneva, 1995
For the latest edition see: JCGM 100 : 2008 (GUM 1995 with minor corrections) Sept. 2008 BIPM.
Reporting to the BIPM international standard guidelines for uncertainty indicates formal quantitative scientific evaluation making it highly likely it is quantitatively reproducible. (k=2 means “Expanded uncertainties giving a confidence level of approximately 95%” i.e. within +/- 2 sigma).
Such documentation of uncertainty is extremely rare in IPCC publications. Climate science would take a major step up if it would begin to quantify uncertainty in all publications in keeping with these international guidelines of BIPM’s GUM – JCGM 100 : 2008.
For a publicly posted paper covering some of the measurement methods (but not as accurately) see: Evaluation of factors affecting accurate measurements of atmospheric CO2 and CH4 by wavelength-scanned cavity ring-down spectroscopy.Nara et al. 2012
David L. Hagen says:
February 28, 2014 at 6:01 am
Thanks a lot for the references!
The WS-CRDS method thus uses extremely narrow IR bands at the peak band of the main isotope of both CO2 and CH4. That makes that the calibration standards may not differ too much in isotopic composition from the target composition, or that can give underestimation or overestimation of the real levels. The same for differences in N2/O2/Ar composition which gives differences in broadening of the CO2 and CH4 bands, thus influencing the peak of 12CO2 and 12CH4… But even so, the changes are very small, in the hundredths of a ppmv…
I wonder if they can detect (sooner or later) the relative abundances of 12CO2 and 13CO2 in the atmosphere from continuous sampling by using narrow IR bands for each individual isotope peak wavelength…
Ferdinand Engelbeen
Paul Brewer et al. used a CRDS from Picarro #G2301. See the G2301 datasheet. They state 25 ppb over 5 minutes with 500 ppb drift/month. Thus the benefit of calibration gases.
PS For another CRDS ref:
13CO2/12CO2 isotopic ratio measurements with a continuous-wave quantum cascade laser in exhaled breath Vasili L. Kasyutich et al.
For wavelength modulation spectroscopy (WMS) see:
UTILIZATION OF MULTIPLE HARMONICS OF WAVELENGTH MODULATION ABSORPTION SPECTROSCOPY FOR PRACTICAL GAS SENSING, Kai Sun DEC 2013, Dissertation
For the potential for reducing satellite measurement uncertainty compared to current see Nigel Fox NPL TRUTHS project. e.g. Seeking the TRUTHS about climate 2011. Paper: Accurate radiometry from space: an essential tool for climate studies Nigel Fox et al. 2011.
David L. Hagen,
Thanks again for the references. Amazing what modern analytical techniques can reach these days.
My last pre-retirement confrontation with such instruments is already 10 years ago and the instrument makers obviously didn’t stop applying new techniques…
Thus my idea to use that for 13C/12C ratio’s is already in use. Again too late for a patent of my own…
This group knows that CO2 atmospheric concentration is around 400 PPM. Mathematically, 400 PPM means that .04% of our atmosphere consists of CO2. Ask people in your work place, lunch room, dinner table, coffee house what they think the percentage of the atmosphere consists of CO2. Regardless of which side of the debate they may be , the answers given are usually off by a magnitude of 100 to 1,000 or more.
We are fighting a battle of public perception more than a battle of the merits of the science. The science is clear. CAGS alarmists have convinced a good part of the world that increased CO2 is causing the earth to warm with catastrophic effects. The earth has not warmed in 17 years, despite continued increases in both the amount and the rate of increase in the amount of CO2. When your results do not meet your prediction, or projection, you are wrong, end of story, thank you Dr. Feynman.
In every article, in every comment on WUWT, and at every opportunity, we should start the discussion with the fact that CO2 is only .04% of the atmosphere. It is much harder for the other team to convince people that CO2 is a problem once the general population understands that CO2 is .04%. What if it doubles? Now it is .08%, still an infinitesimal amount. One comment said that new technology can measure CO2 concentrations +/- .04%. This means that we can detect a change in co2 concentration of .000016%. While quite a technological achievement, the ability to measure such small changes of a trace gas does not have any meaning, and does not present any useful information in the real world.
I would like to ask our gracious host, to always express CO2 concentration in percentage terms, in addition to the more scientific expression, ie 400 PPM (.04%) so that the numerically challenged in our society can better appreciate the tiny amount of CO2 that is purported to cause such a potential catastrophe.
Bill Sprague says:
February 28, 2014 at 1:03 pm
Bill, the tiny percentage of CO2 in the atmosphere is a non-argument. The same percentage of hydrogen cyanide in the atmosphere will kill most animals… It is a matter of what the effect is of such a percentage.
In the case of CO2, the effect is small: the doubling of CO2 from 280 to 560 ppmv will increase global temperatures with not more than 1°C, not a disaster, mainly beneficial for all plant life. The rest of the “projections” is based on failed climate models. That is the message we need to bring to the masses: that all disaster scenario’s are based on models, not more real than the movies from the Holywood industry…
Ferdinand,
Thank you for your comment, and I completely understand your argument. Your argument is scientific. My argument is public persuasion and perception. The public perception is that CO2 is 20% of the atmosphere, headed to 40%, and we are all going to die. My point is that 400 PPM sounds like a lot, because 400 is a big number, and is either a car payment or even a house payment for some. Ask John Kerry what percentage of the atmosphere is CO2. I doubt that he knows, and I doubt that he could explain in layman’s terms to other laymen that .04% is something to worry about.
Yes, we also need to point out the inaccuracy of the models. The difficulty is that Scientist A says yes they are and Scientist B says no they are not, and the public does not have enough education to tell the difference on their own. They hear that 97% of scientists agree that CAGS is real and government needs to “do something” fund windmills, solar, etc etc. My point is not one based on science, although the science is on our side. It is based on the simplistic logic that CO2 is only .04% of the atmosphere, so what are you worried about. It is 4 pennies out of $10,000 dollars.
It is to speak to the general public in a readily comprehensible way. The genius of Michal Mann was the hockey stick, a simple, visual depiction of runaway CO2 associated with runaway temperatures. The reality is that if his hockey stick were the prize in a box of Cracker Jacks, it would be too small to find, and the customer would feel cheated, because he did not get his prize.
Englebeen and Hagen above did an excellent job of explaining the need for and use of reference gasses – thanks, guys!
The concern by others that the availability of new standards is going to somehow change CO2 measurements is completely misplaced. As I read the release, it’s just announcing the development of a reliable method of creating secondary reference standards for atmospheric gas measurement, in response to greatly increased demand for such standards. This happens in metrology all the time; there are primary, secondary, and tertiary standards, and the aim is always to make each successive generation of standard match the higher levels as closely as possible. Verifying that is simply a matter of comparing the standards with each other with the most sensitive equipment available.
In this case, it doesn’t matter a whole lot where and when the primary atmosphere standard was gathered; as mentioned earlier, calibrations are most likely done at bottom, mid and top-scale, and I’d be extremely surprised if there was any significant non-linearity inherent in the instruments’ designs, in any proximity to the values actually being measured.
This is seriously a non-issue relative to CO2 monitoring and the climate debate: All it means is that it’ll be easier and cheaper to calibrate the measuring instruments more accurately. – And as noted by someone else above, the current level of accuracy is far greater than any level that would impact the climate debate, on the order of small fractions of a percent of a value that we’re concerned about doubling.
I have often wondered why they measure CO2 on top of the largest active volcano on the planet. Not to mention it’s on an island in the middle of the Pacific Ocean which is the largest producer of CO2 on the planet.
elmer says:
March 1, 2014 at 5:38 am
I have often wondered why they measure CO2 on top of the largest active volcano on the planet.
The first continuous measurements in fact were at the South Pole, but as that has a gap of a few years, the Mauna Loa measurements are the longest continuous series on the planet. But there are a lot of places nowadays where CO2 and other trace gases are measured, see:
http://www.esrl.noaa.gov/gmd/dv/iadv/ already mentioned by Billy Liar.
They all show similar CO2 levels within natural variability (mainly seasonal).
Winds at the 3,400 m level of the station are mainly trade winds free from local pollution, but if there are downslope winds bearing CO2 from volvanic vents (or slightly CO2 depleted upslope winds from the valleys), these are excluded from daily to yearly averaging.
Some 20 ppmv/year CO2 (40 GtC) comes out of the equatorial waters and are absorbed near the poles. That are mainly continuous flows which hardly affect local levels. Without any mixing by winds, that would increase the local level at Mauna Loa with some 0.05 ppmv/day, but as there are near always winds…
A paleo-fact(or) to keep in mind is that the oxygen in the atmosphere was originally stripped from CO2. I.e., there was more than 20% CO2, and plants (including algae and early bacteria) reversed the ratios by eating it! What a massive pig-out that was.