Guest Post by Willis Eschenbach
In 2006, I lived for a year in Waimea, on the Big Island of Hawaii. From my house I could see the Mauna Loa Observatory (MLO). This observatory is the home of the longest continuous series of CO2 measurements we have. The recording station was set up by Dave Keeling in 1959, and has operated continuously ever since.
Figure 1. Mauna Loa Observatory ( 19.536337°N, 155.576248°W)
Here’s a view of the observatory:
Every time the subject of CO2 measurements comes up, people raise all kinds of objections to the Mauna Loa measurements. So I thought I’d start a thread where we can discuss those objections, and perhaps dispose of some of them.
Here are the objections that I hear the most:
1. The Mauna Loa results don’t measure the background CO2 levels.
2. You can’t get accurate CO2 measurements from samples taken on the side of an active volcano that is outgassing CO2.
3. The measurements from Mauna Loa are not representative of the rest of the world.
4. What about the Beck data, doesn’t it contradict the MLO data?
5. Keeling chose a bad location.
Before we get into those issues, let’s start by looking at the local meteorological conditions at the site. Mauna Loa is at an elevation of 3397 metres (11,140 ft) on the side of a 4,170 metre (13,680 ft) volcano way out in the middle of the Pacific Ocean. Because it is on an island, it gets the “sea breeze” in the daytime, and the “land breeze” in the nighttime.
These winds are caused by the differential heating of the land and the sea. Land heats up much faster than the ocean. So during the day, the warmer land heats the air, which rises. This rising air is replaced by air moving in from the surrounding ocean, creating the “sea breeze”.
At night, the situation is reversed. The land is cooler than the ocean. This cools the air. The cool air runs downhill along the slopes of the island and out to sea, creating the “land breeze”. Here’s a drawing of the situation:
Figure 2. Day and night breezes at Mauna Loa.
Now that we understand what is happening at Mauna Loa, let’s look at the objections.
1. The Mauna Loa results don’t measure the background CO2 levels. As you might imagine from Fig. 2, the CO2 measurements are taken only at night. Thus, they are measuring descending air that is coming from thousands of feet aloft. This air has traveled across half of the Pacific Ocean, so it is far from any man-made CO2 sources. And as a result, it is very representative of the global background CO2 levels. That’s why Keeling chose the site.
2. You can’t get accurate CO2 measurements from samples taken on the side of an active volcano that is outgassing CO2. This seems like an insuperable objection. I mean, Mauna Loa is in fact an active volcano that is outgassing CO2. How do they avoid that?
The answer lies in the fact that the volcanic gasses are very rich in CO2. At night, they are trapped in a thin layer near the ground by a temperature inversion.
To detect the difference between volcanic and background CO2, the measurements are taken simultaneously from tall towers and from near the ground, at intervals throughout the night. Background CO2 levels will be around 380 ppmv (these days), will be steady, and will be identical at the top and bottom of the towers. Volcanic gasses, on the other hand, will be well above 380 ppmv, will be variable, and will be greater near the ground than at the top of the towers.
This allows the scientists to distinguish reliably between volcanic and background CO2 levels. Here is a description of the process:
Air samples at Mauna Loa are collected continuously from air intakes at the top of four 7-m towers and one 27-m tower. Four air samples are collected each hour for the purpose of determining the CO2 concentration. Determinations of CO2 are made by using a Siemens Ultramat 3 nondispersive infrared gas analyzer with a water vapor freeze trap. This analyzer registers the concentration of CO2 in a stream of air flowing at ~0.5 L/min. Every 30 minutes, the flow is replaced by a stream of calibrating gas or “working reference gas”. In December 1983, CO2-in-N2 calibration gases were replaced with the currently used CO2-in-air calibration gases. These calibration gases and other reference gases are compared periodically to determine the instrument sensitivity and to check for possible contamination in the air-handling system. These reference gases are themselves calibrated against specific standard gases whose CO2 concentrations are determined manometrically. Greater details about the sampling methods at Mauna Loa are given in Keeling et al. (1982) and Keeling et al. (2002).
Hourly averages of atmospheric CO2 concentration, wind speed, and wind direction are plotted as a basis for selecting data for further processing. Data are selected for periods of steady hourly data to within ~0.5 parts per million by volume (ppmv); at least six consecutive hours of steady data are required to form a daily average. Greater details about the data selection criteria used at Mauna Loa are given in Bacastow et al. (1985). Data are in terms of the Scripps “03A” calibration scale.
There is a more detailed description of the measurement and selection process here.
As a result, the Mauna Loa record does accurately measure the background CO2 levels, despite the fact that it is on an active volcano. The samples that are identified as volcanic CO2 are not thrown away, however. They are used for analyses of the volcanic emission rates, such as this one (pdf).
3. The measurements from Mauna Loa are not representative of the rest of the world. Well, yes and no. The concentration of atmospheric CO2 varies by month, and also by latitude. Here is a “carpet diagram” of the changes by time and latitude.
Figure 3. A “carpet diagram” of CO2 distributions, by time and latitude.
Note that the swings are much greater in the Northern Hemisphere. Presumably, this is from the plants in the much larger land area of the Northern Hemisphere. However, the difference between the annual average of the Northern and Southern Hemispheres is small. In addition, there are smaller daily variations around the planet. An animation of these is visible here, with day by day variations available here.
Figure 4 shows is a typical day’s variations, picked at random:
Figure 4. Snapshot of the variations in tropospheric CO2. Note that the range is small, about ±1% of the average value.
In general, the different global records match quite closely. In addition to the Mauna Loa observatory, NOAA maintains CO2 measuring stations at Barrow, Alaska; American Samoa; and the South Pole. Here is a comparison of the four records (along with two methane records):
Figure 5. Comparison of the CO2 records from the four NOAA measuring sites.
As you can see, there is very little difference between the CO2 measurements at the four stations – two in the Northern Hemisphere, two in the Southern, two tropical, and two polar.
4. What about the Beck data, doesn’t it contradict the MLO data? In 2007, Ernst-Georg Beck published a paper called “180 Years Of Atmospheric CO2 Gas Analysis by Chemical Methods” (pdf). In it, he showed a variety of results from earlier analyses of the atmospheric CO2. In general, these were larger than either the ice core or the MLO data. So why don’t I believe them?
I do believe them … with a caveat. I think that the Beck data is accurate, but that it is not measuring the background CO2. CO2 measurements need to be done very carefully, in selected locations, to avoid contamination from a host of natural CO2 sources. These sources include industry, automobiles, fires, soil, plants, the list is long. To illustrate the problems, I have graphed the Beck data from his Figure 13, against the Law Dome ice core data and the MLO data.
Figure 6. CO2 data from a variety of sources. White crosses are MLO data. Three separate ice core records are shown. Photo is of Mauna Loa dusted with snow (yes, it snows in Hawaii.) PHOTO SOURCE
There are several things to note about this graph. First, there is good agreement between the Law Dome ice core data and the MLO data over the ~ two decade overlap. Second, there is good agreement between the three separate Law Dome ice core datasets. Third, both the ice cores and the MLO data do not vary much from year to year.
Now look at the various datasets cited by Beck. Many of them vary quite widely from one year to the next. The different datasets show very different values for either the same year or for nearby years. And they differ greatly from both the ice core and the MLO data.
Because of this, I conclude that the Beck data, while valuable for showing ground level CO2 variations at individual locations, do not reflect the background CO2 level of the planet. As such, they cannot be compared to the MLO data, to the ice core data, or to each other.
5. Keeling chose a bad location. I would say that Keeling picked a very good location. It not only allows us to measure the background CO2 in a very accurate manner, it provides invaluable information about the amount of CO2 coming from the volcano.
My conclusion? Most of the records in the field of climate science are short, spotty, and not very accurate. We have little global historical information on ocean temperatures, on land temperatures, on relative humidity, on atmospheric temperatures, on hurricane occurrence and strength, or on a host of other variables. By contrast, the Mauna Loa CO2 records are complete since 1959, are very accurate, and are verified by measurements in several other locations.
I’m about as skeptical as anyone I know. But I think that the Mauna Loa CO2 measurements are arguably the best dataset in the field of climate science. I wouldn’t waste time fighting to disprove them, there are lots of other datasets that deserve closer scrutiny.
[UPDATE] A reader below has added another question, viz:
6. What about Jaworoski’s claim that the ice core data has had its age “adjusted”?
Jaworoski argues that the age of the air in the ice cores has been “adjusted” to make it align with the modern data. He says, for example, that the Siple ice core data has been moved forwards exactly 83 years to make them match the Mauna Loa data.
Dating the ice core data is problematic. We can date the ice itself pretty accurately, through counting layers (like tree rings) and through studying various substances such as volcanic dust that is trapped in the ice. However, dating the air is harder.
The difficulty is that the air is not trapped in the ice immediately. The pores in the “firn”, the snow that falls annually on top of the ice are open. Air can flow in and out.
As more and more snow falls over the years, at some point the pores close off and the air is trapped. So how long does it take for the pores in the firn to seal off?
Unfortunately, as in so many areas of climate science, the answer is … “depends”. It depends inter alia on how much snow falls every year, how much of that snow sublimates (changes from a solid to a gas) every year, and even the shape and size of the individual snowflakes.
The end result of all of this is that we end up with two ages for any given thin slice of an ice core. These are the “ice age” (how old the ice itself is), and the “air age” (how old the air trapped in the ice is). The ice is always older than the air.
The main variable in that is thought to be the annual snowfall. Unfortunately, while we know the current rate of annual snowfall, we don’t know the historical rate, particularly tens of thousands of years ago. So we use the concentration of an isotope of oxygen called “d18O” to estimate the historical snowfall rate, and thence the firn closing rate, and from that the air age.
Sounds a bit sketchy? Well … it is, particularly as we go way back. However, for recent data, it is much more accurate.
So to bring this back to real data, in the ice core data I showed in Fig. 5, the air is calculated to be 30 years younger than the ice for cores DEO8 and DEO8-2, and 58 years younger for the DSS core. Is this correct? I don’t know, but I do know that there are sound scientific reasons for the “adjustment” that Jaworowski objects to .
Finally, the existence of a thirty to sixty year difference in air and ice age doesn’t make much difference in the pre-industrial levels of CO2. This is because prior to about 1800, the level is basically flat, so an error in the air age dating doesn’t change the CO2 values in any significant manner.
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Tony says:
June 5, 2010 at 10:56 am
You are corret about the outgassing when water changes states.
In addition, the diffusion of CO2 through ice was determined recently at Scripps Oceanographic Institute.
The diffusion, of course, depends on initial concentration, going from high to low, directly proportional to that concentration. Fick’s Laws.
If it were very high in ice cores in the past, it would be much lower than that when measured after millenia have passed. The concentration in ice bubbles at Vostok and other places, therefore, has a systematic bias that disfavors high initial concentrations being preserved. If the [ ] were similar, or lower to that today, diffusion would stop (actually equilibrate, with molecules going back and forth). The concentration inside always seeks the outside concentration.
Altogether, the ice samples from cores is an unreliable proxy, the longer the time, the more the measured value is distorted. So when we measure ancient bubbles showing 10,000 ppm, for example, it might have been an order of magnitude higher when measured today, depending on the diffusion path distance (distance till the outside atmosphere is reached).
This can be calculated for each path distance, since the diffusion constant is now known, thanks to Scripps.
Richard S Courtney says:
June 5, 2010 at 3:13 am
Hawaii lies in the trade winds belt. Typical wind is about 15 knots, increasing aloft. This means that any CO2 that moves aloft during the day will be miles and miles away when the air is descending during the night.
As the quotation I provided says, they wait until they have stable measurements (less than 0.5 ppmv change) before measuring. I’d call that reliable.
Thanks, Richard, science is in large measure debate and discussion, your ideas are always welcome.
Having said that, I object strongly to the idea that the background CO2 level is “mythical”. It is measured at places from the Arctic to the Antarctic, and in the tropics as well. It is also measured by satellite (see Fig. 4). We can see how this background level changes with the seasons, and with the latitude (see Fig. 3).
So in what conceivable sense can it be called “mythical”? Yes, as you say, what this means for radiative forcing is an open question. But the background level itself is very real, and not mythical in any way.
My thanks to you,
w.
This appears to be similar to Urban Heat Island effect, measured with a CO2 scale. Perhaps a Global Urban Carbon effect. I like the data, I don’t think they’re using it to monitor what it really reflects.
wayne says:
June 5, 2010 at 3:23 am
Well, I had discovered some truly remarkable aspects which the margin of this blog post is too small to contain …
Seriously, I can only cover so much. I wanted to keep it focused on the validity of the CO2 record, and not wander afield into the reasons for the swings in the record.
Willis Eschenbach says:
June 5, 2010 at 10:59 am
Actually you describe dissolution rather than diffusion. This depends on the interfacial thermodynamics and kinetics.
Once into the ice, then diffusion procedes according to Fick’s Laws.
An example of this is water diffusing into oil. First, the oil has to become “wetted” for an intimate contact before the water diffuses into the oil (to only parts per million concentration, certainly). This is the inerfacial boundary problem. Since we are talking about long time periods, the dissolution rate is not limiting, so my point becomes moot, actually. I am just making a technical point for accuracy.
Some materials have low dissolution rates, but high solubilities or high diffusivity (another term that relates to the diffusion constant, or diffusion rate).
Daniel H says:
June 5, 2010 at 3:34 am
Thanks, Daniel. You are correct. The measurement is done continuously. However, the overwhelming majority of the samples that are actually deemed good enough to be used are night-time samples. From the excellent link you cited, here is their discussion of the criteria that touches on the day-night issues:
You have raised good points,
w.
Richard S Courtney says:
June 5, 2010 at 3:34 am
Richard, while that is an important issue, I’d like to ask that you discuss it on another thread. This thread is about whether the Mauna Loa record is valid, not about whether humans are the cause of the changes in the background levels.
A sea breeze/land breeze only sets up if the island is under a weak pressure gradient. The subtropical high roughly located between 20-40 degrees latitude is generally too strong thus the island sits under trade wind flow around the subtropical high. This high has to migrate away from the island or weaken for a sea breeze/land breeze to set up. I’m not saying it doesn’t happen but it definitely doesn’t happen everyday
Tom in Florida says:
June 5, 2010 at 6:28 am
You’re just trying to taunt me, I’m living in the US now and there’s only cold-water shark infested surfing here … which as a tropical boy I’ll pass on. Meanwhile, at Frigates Pass in Fiji, my old spot, the waves are likely cranking, with the aforementioned warm tropical offshore breeze blowing … sigh …
OK. No more comments on surfing, that’s just mean.
Gail Combs says:
June 5, 2010 at 6:30 am
Not sure what you mean by “lumpy”. As I commented in the head post, the background levels vary by only about ±1% around the globe at any given instant, which is hardly “lumpy” in my book. It looks like more because of the colors used, but check out the legend, we’re only talking a few ppmv.
HankHenry says:
June 5, 2010 at 6:42 am
Basically, yes. At ground level there are lots of CO2 sources and sinks. Aloft, the gas is pretty well mixed (±1%).
Unknown, because the effect of CO2 on temperature in general is unknown.
Willis
Thanks for a well written exposition.
I wrote an article on ‘Historic variations in Co2 measurements ‘ which was carried over at the Air Vent a couple of months ago.
http://noconsensus.wordpress.com/2010/03/06/historic-variations-in-co2-measurements/
My article was primarily concerned with ascertaining the history behind the measurements and the part played by the science in every day life. It carried numerous links putting the case for and against the likely accuracy of these historic measurements, which were often carried out by very fine scientists using increasingly sophisticated methods.
Together with the numerous links, arguments and counter arguments put by posters-including many of those posting here in response to the excellent article by Willis-I think it is probably the most comprehensive library of CO2 material on this subject available in one place anywhere on the net.
In the interests of completeness and even handedness I will add this thread to it.
As I say, I am more interested in the history behind the readings than the scientific merits for the claims made by such as Ernst Beck. However, I think we do the old time scientists a disservice by believing that even after some 130 years of measurements they still didn’t know what they were doing.
A lot of this argument depends on how much co2 is outgased by the oceans and returns to it, how quickly this happens and the general residence life. Is it ten years as some claim, or up to 1000 years for the residual portion as the IPCC asserts?
If the Northern and Southern Hemisphere oceans were in outgasing phase during one of the numerous warm spells that occurred even during the little ice age-some of the CO2 measurements recorded in the period 1830 to 1955 are not at all outlandish.
I tend to agree with Richard S Courtney’s comments here. I am 55% sure (and I put it no higher than that) that the historic measurements have something valuable to tell us, and whilst many can be easily dismissed a proportion have enough credibility to warrant independent auditing.
Tonyb
Willis,
Is it just me, or does your “Figure 4. Comparison of the CO2 records from the four NOAA measuring sites.” chart show a decrease (or at least little change) in CO2 during the “new ice age” scare of the late 70’s ?
Seems to be no sign of it in your Figure 5.
Why do “all” the scary trends start after the late 70’s ?
The snow in Chicago in the late 70’s, was so deep that people put flags on their antennas, so other drivers could see them coming at intersections.
Ah, the good old days.
Pamela Gray says:
June 5, 2010 at 7:09 am
Pamela, good questions as always, not sure I can answer them.
The relative effect of the “greening” of the planet is part of a larger question of where the non-anthropogenic CO2 sources and sinks are located. This is not well understood.
Not sure what your point is here.
CO2 is trapped near the ground only in certain circumstances. However, it does not have to be high up in the air to absorb and emit radiation. My bible, Geiger’s “The Climate Near the Ground”, states that about three quarters of the downwelling radiation striking the ground comes from the bottom 90 metres (300 ft) of the atmosphere.
If you look at the mid-tropo CO2 and temp anomalies from July 2009, you can see the general jet stream position for that month. It was a very cool month(record cool for some) as a trough setup over the eastern half of the US. Higher Co2 south of the jet with the warmer temps from surface into upper atmosphere. The smearing of the yellows into the Upper Midwest were due to the brief warmups we encountered. I looked at archived weather maps for the month. Just an interesting tidbit to the discussion.
http://www.nasa.gov/images/content/411791main_slide5-AIRS-full.jpg
http://www.hprcc.unl.edu/products/maps/acis/Jul09TDeptUS.png
Charles Higley says:
June 5, 2010 at 9:11 am
While one might “expect atmospheric CO2 to fluctuate”, the records from Mauna Loa, American Samoa, Barrow, and the South Pole all agree that such fluctuation has not happened in the last half century. In fact, other than the annual swings, there has been a slow rise and the data is remarkably stable.
So while you might believe that there was some huge swing in background CO2 levels just prior to when we started accurate measurements, I doubt it. Among other things, you should run the calculation on the number of gigatonnes of CO2 that would have to be emitted to create such a swing … very doubtful.
I guess since I am a diffusion expert in my career, I will add one more wrinkle.
Diffusion according To Fick’s Laws also pertains to gases in gases.
The Mauna Loa method measures frequently and dismisses outliers (rejects them according to some arbitrary rules relying on operational reasons, not entirely upon statistical reasons).
OK. However, the volcano business worries me immensely because there is a sink with parts per hundred! of CO2 right nearby. Forget about the winds, and assume for a moment the air is static. Imagine concentric spheres around the volcanic CO2 emanation point. The CO2 diffuses into surrounding air into each sphere, with concentration decreasing in half with each diameter added, since the concentration is directly proportional to distance traveled. By the time it reaches the measuring venue, it becomes proportionally less, but it is a positive contributor!. It may be large or small, but remember we started at parts per hundred, 10,000 times the concentration at the measurement point.
This is a classic case of introduction of systematic error or bias.
One experiment to do is to perform inverse isotopic dilution. Release a cannister of 14C CO2 at the volcano vents periodically and count the radioactivity. Or, if people are afraid of 14C, they can use 13C and do GC mass spec.
Then, we can know the amount of systematic error after several experiments under different conditions. It may be large, or small, but it has to be something!
This is why it would be great if it were not a volcano setting!
Tony says:
June 5, 2010 at 10:56 am
See here for what the adherents of this theory say.
Mr. Eschenbach,
Your essay gives me the opportunity to ask a question that I hope some brilliant sceptic, such as yourself, will take up. I realize that your essay is about measuring CO2 concentrations and I have no quarrel with what you say. My concern is that you give a pass to Warmists who invariably use one or another “a priori” assumption in their so-called science. In this case, the “a priori” assumption is that CO2 molecules are distributed randomly throughout the atmosphere. I am not aware of experiments undertaken to show that CO2 is distributed randomly. Nor am I aware of experiments undertaken to show that there are rivers of CO2, marshes of CO2, or whatever one might imagine. To my mind, the assumption that CO2 molecules are randomly distributed is something like an assumption that might have been held in the early days of navigation on the Mediterranean. Those early sailors might very well have assumed that all oceans behave as the Mediterranean does. They might not have imagined the existence of the Gulf Stream, El Nino, and similar phenomena. Why should they have imagined them? Only experimentation, actual travel on all the oceans of the world revealed such phenomena. So, why do we simply assume that CO2 is randomly distributed? Why are we not creating the multitude of observation stations which might reveal that Earth’s atmosphere contains something like a Gulf Stream of CO2? Let’s not be mislead by the magnitudes. I am not suggesting that there is something on the scale of a Gulf Stream, but something of lesser magnitude that is of importance in CO2 measurements for Earth’s atmosphere.
So what do we do with this CO2 “concentration” information and what does it imply about the operation of a complex ecosystem? Let’s take a non CO2 example – say phosphorous in a freshwater river with agriculture and development inputs. If one samples to derive the river’s phosphorous concentrations at various points- we may find they remain within a fairly tight annual range. If we add in flow however- we may see P loading change by orders of magnitude on a daily, annual and inter-annual basis. (Sources of P are numerous and the contribution of any given source can change on a month to month and year to year basis.) If we measure below a shallow impoundment in the summer we may see a significant relative reduction in both P concentration and loading. (Rooted vegetation has the capacity for luxury uptake of P- the ability to store many times its P needs and “starving” the competition of this needed building block.) However the algae may dominate early and diminish the light penetration required by the macrophytes allowing more P bleed through- so we can have two different concentration outputs for the same input. If we measure P in late fall we could see a pulse of P from reservoir turnover or die back of the terrestrial vegetative cover. If we measure in the spring we could see another turnover P pulse or perhaps some suppresion of P from early algae blooms. If we measure in the winter we may not see as much P change- once the ground froze and how much of the agricultural land was planted in winter or cover crops. There may be year to year P changes as the result of alkalinity, temperature, rainfall patterns, ice patterns, wind patterns, crop mix, turnover P flux and the chaotic interplay between algae and macrophytes for system dominance. Plus others we never contemplated. A P mass balance for this relatively “simple system” is complex and non-predictive. “Concentration” actually may tell us very little about what is happening within the system and future system adaptations. My very long winded point-concentration is just the start in understanding how little we know-and because of sensitivity to initial conditions- can know.
Now the management implications of P. Do we spend millions of dollars to upgrade a wastewater treatment facility to remove P? The answer – it depends. Politicians and media hate the short answer and have no tolerance for a longer more complicated response. Regulators make it simple- they create a one size fits all concentration standard making the politicians, bureaucrats and media happy. We no longer have to worry about the diverse sources of P – only SOME human P . Nor do we need to concern ourselves with the complex consequences. We now have a simpler and more perfect world- humans discharging P (and only those using a pipe) above the decreed limit is bad and below is good. Problem solved.
Sound familiar?
Willis Eschenbach
June 5, 2010 at 11:58 am
Hi Willis:
I am amazed with the 1,2,3 ,4 statements you are quoting.
Are they making a dress from a pattern? Talk about cherry picking data.
particularly
4. In keeping with the requirement that CO2 in background air should be steady, we apply a general “outlier rejection” step, in which we fit a curve to the preliminary daily means for each day calculated from the hours surviving step 1 and 2, and not including times with upslope winds. All hourly averages that are further than two standard deviations, calculated for every day, away from the fitted curve (“outliers”) are rejected. This step is iterated until no more rejections occur.
On the lines:” you will obey me, or else”
They have a preconceived notion of what the curve should be and they impose it, is my conclusion from this series.
You say there are independent measurements. Once I had managed to find a link and publications for those measurements. The were all Keeling and another fellow,possibly the graduate student going through the loops. I do not call that independent.
The satellite data show large variations and lumps as they said themselves in AIRS, and this against the current orthodoxy of well mixed and background. God only knows whether it affected their data interpretation.
Let me try again to express what I mean with the temperature analogy:
Temperatures are not the true energy measure. To get the energy of the system one would have to integrate over the whole globe, using emissivities and gray body shapes.
ppm of CO2 in any specific location are not indicative of the amount of CO2 in the atmosphere, one would have to integrated all the variations in three dimensions to get the amount of CO2 in the air.
Here are the locations I find:
http://scrippsco2.ucsd.edu/data/atmospheric_co2.html
something like 14, and practically all the publications are Keeling et al
There is a map too
http://scrippsco2.ucsd.edu/research/atmospheric_co2.html
Do you believe that these 14 or so stations are representative enough so that the measurements could produce the amount of CO2 in the atmosphere?
Going where the air is “pure” defeats the purpose of measurement because it is the total amount of CO2 that would be working for the greenhouse effect, not in the pure and in the rarefied atmosphere.
Steve Fitzpatrick says:
June 5, 2010 at 11:06 am
For me, it’s never a waste of time to put out a clear explanation of what I see as the “truth” (a relative term, yes, I know). While there are lots of folks out there who are in the “My mind is made up, don’t bother me with the facts” headset, there are also large numbers of people who are seriously trying to understand what is going on. I think that they are what might be called the “forgotten majority”, they get all of this nonsense from the pro-AGW side (and some from skeptical side as well), and they are not clear on what is valid and what isn’t.
So I think that clear explanations of things never go amiss.
p.s. This business of up winds and down winds is confusing.
How can there be an inversion layer in a down wind?
If the up wind is 14 knots, the downwind should also be 14 knots and bring back the CO2.
Actually we observe this terrible effect in Attica, in Greece on days where there are no highs or lows moving into our area the up winds and down winds from the sea to land and vice verso reign supreme. The result is that coming into Piraeus port in the evening one sees a low long yellow pollution cloud over the sea and in the morning it comes right back in and goes up trapped next to the 2000 meter mountains, building up the polution to incredible levels if the motionless days continue.
It is interesting that this is reflected in greek mythology, because the fires of Athens would pollute even three thousand years ago. They married off a princess to the North Wind, so that he would keep the city air clear.
Willis,
You say “This thread is about whether the Mauna Loa record is valid”
Assuming that the point of the observatory is to measure and report the ‘background level’ in terms of less than 1 part of Co2 in a million parts of a mixed gas, I still have my doubts. I can articulate only a few at this point;
– The measurement expressed in ppm means that, of a flow of air at x molecules/second, y of those molecules were CO2. How do they measure the x molecules/second? They must control the flow of air, and also the calibration gases, of the equivalent of a million molecules per second to within less than 1 molecule/second How do they do that?
-And as temperature has a huge effect on the density of gases, and hence pressure, and hence the molecule flow-rate, how do they keep the temperature within the limits needed to preserve the accuracy to less that 1 in a million?
– If the proportion of other gases in the air changes, but the number of CO2 molecules remains the same, would the instrument readings change? If so, then we could be seeing artefacts. (I see methane mentioned; what effect would a few ppm of methane have, in the gas stream? Or a change in the number of Xenon molecules?)
– Does the rejection algorithm introduce a bias? We would only need a tiny bias over the thousands of readings to add a millionth .. which is getting on for half of the claimed yearly increase of 3 parts per million in the ‘backgound’ (aka ‘average’) figure.
– Why isn’t all the data used and statistically treated to find the various averages? Otherwise there is a suspicion of cherrypicking.
– Why aren’t there other Co2 instruments being used at the observatory? If the Keeling instrument is so sensitive and well-calibrated, then it must be a good reference instrument over the whole range of its actual output (and not just the ‘useable’ bits) This apparent absence of other reference instruments at the site is a mystery.
Steven and Steve,
The last line in the quotation below is completely inaccurate. There is no part of the atmosphere that is opaque to mid-ir. Clouds and other forms of non-gaseous water in the atmosphere, as well as particulates, can be total-absorbing for a large portion of the mid-ir spectrum. But the statement below is still inaccurate.
A simple experiment to confirm this is on an FT-IR spectrometer. Monitor a simple interferrogram, open the cover, and breathe into the sample chamber. You will see an increase in the sharp absorbtion doublet for carbon dioxide and in all of the wide bands for water vapor. Both of those gasses comprise several percent of your exhaled breath.
Steven mosher says:
June 5, 2010 at 9:44 am
“Steve Fitzpatrick says:
June 5, 2010 at 8:47 am
Hi Willis,
Having been through this argument several times on different threads, I have concluded that it may be impossible to make progress on this subject with many who comment; they seem immune to influence by data or reasoned analysis. ”
It’s such a waste of energy to engage them. I was glad you added this. They seem to forget the fundamentals. Everybody should know this
“The only CO2 concentration that matters in terms of radiative forcing is the concentration high in the atmosphere. CO2 concentration near sea level makes no difference, since the lower atmosphere is essentially opaque to infrared at the wavelength where CO2 absorbs.”