Here’s an interesting Q&A on issues with trying to determine the SAT of the Earth that I have not seen before. There’s a surprise at the end as to who wrote it.
Q. What exactly do we mean by SAT ?
A. I doubt that there is a general agreement how to answer this question. Even at the same location, the temperature near the ground may be very different from the temperature 5 ft above the ground and different again from 10 ft or 50 ft above the ground. Particularly in the presence of vegetation (say in a rain forest), the temperature above the vegetation may be very different from the temperature below the top of the vegetation. A reasonable suggestion might be to use the average temperature of the first 50 ft of air either above ground or above the top of the vegetation. To measure SAT we have to agree on what it is and, as far as I know, no such standard has been suggested or generally adopted. Even if the 50 ft standard were adopted, I cannot imagine that a weather station would build a 50 ft stack of thermometers to be able to find the true SAT at its location.
Q. What do we mean by daily mean SAT ?
A. Again, there is no universally accepted correct answer. Should we note the temperature every 6 hours and report the mean, should we do it every 2 hours, hourly, have a machine record it every second, or simply take the average of the highest and lowest temperature of the day ? On some days the various methods may lead to drastically different results.
Q. What SAT do the local media report ?
A. The media report the reading of 1 particular thermometer of a nearby weather station. This temperature may be very different from the true SAT even at that location and has certainly nothing to do with the true regional SAT. To measure the true regional SAT, we would have to use many 50 ft stacks of thermometers distributed evenly over the whole region, an obvious practical impossibility.
Q. If the reported SATs are not the true SATs, why are they still useful ?
A. The reported temperature is truly meaningful only to a person who happens to visit the weather station at the precise moment when the reported temperature is measured, in other words, to nobody. However, in addition to the SAT the reports usually also mention whether the current temperature is unusually high or unusually low, how much it differs from the normal temperature, and that information (the anomaly) is meaningful for the whole region. Also, if we hear a temperature (say 70°F), we instinctively translate it into hot or cold, but our translation key depends on the season and region, the same temperature may be ‘hot’ in winter and ‘cold’ in July, since by ‘hot’ we always mean ‘hotter than normal’, i.e. we all translate absolute temperatures automatically into anomalies whether we are aware of it or not.
Q. If SATs cannot be measured, how are SAT maps created ?
A. This can only be done with the help of computer models, the same models that are used to create the daily weather forecasts. We may start out the model with the few observed data that are available and fill in the rest with guesses (also called extrapolations) and then let the model run long enough so that the initial guesses no longer matter, but not too long in order to avoid that the inaccuracies of the model become relevant. This may be done starting from conditions from many years, so that the average (called a ‘climatology’) hopefully represents a typical map for the particular month or day of the year.
Q. What do I do if I need absolute SATs, not anomalies ?
A. In 99.9% of the cases you’ll find that anomalies are exactly what you need, not absolute temperatures. In the remaining cases, you have to pick one of the available climatologies and add the anomalies (with respect to the proper base period) to it. For the global mean, the most trusted models produce a value of roughly 14°C, i.e. 57.2°F, but it may easily be anywhere between 56 and 58°F and regionally, let alone locally, the situation is even worse.
Source is here
h/t to: Nick Boyce
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Let’s try again
(-273.15 +2.7) C
Jarryd Beck says:
August 14, 2013 at 2:54 pm
So if they know that there are so many uncertainties, then why are they still pushing alarmism?
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Because the discussion is ideological and theological and not scientific. They believe, and they want to believe because it fits their world view.
That’s what you really want. but life is not burger king and you cant have it your way.
Nor do we have to forced to eat your shit sandwich
. . . . . and at very few of the data points in any of the whole grid are relative humidity or any other variables measured and or used to provide a true indication of actual energy content . . . . This post has finally spelled out just how utterly INSANE the whole debate about global warm. . . er, I mean global climate change has been!! And to think that the whole debate eventually boils down to a question of what to do about a 0.1 degree C change on a mishmashed guestimate of a variable that doesn’t come close to representing average energy (as though that would even mean anything) for a global system that is completely self regulating anyways, and always has been!
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I’m sure he wrote this as a way to puff up just how herculean his job is, but instead, I’m left astounded that Gavin would publish this frank admission of just how utterly meaningless the whole exercise is! I hate the fact that we are paying millions in tax money to keep this !@ur momisugly#*&$*#& charade they have the audacity to call “science” going. This is not the NASA I grew up respecting! Shut it all down! It serves absolutely NO USEFUL PURPOSE.
To be sure, GAT is not particularly meaningful as a scientific measure of the state of the global climate system. Temperature is, after all, an intensive, nonconservative metric that is highly volatile near the Earth’s surface. Nevertheless, it’s there that humanity lives and experiences its impact. And GAT, obtained as an areal average of air measurements at the WMO standard height of 1.5m, is nowhere near as arbitrary as GISS portrays it. The convergence to a distinct time-history of variation during the 20th century is remarkably rapid when only properly vetted, intact station records are employed. The practical (and propaganda) value is unmistakable!
Satellite measurements, on the other hand, can establish in principle the TOA balance between incoming and outgoing radiation. There are formidable obstacles in practice, however, with discrepancies between satellites often far exceeding in their magnitude the sought-after signal of planetary power flux. The latter, alas, is not uniquely related to GAT. Thus the surface integral of the fourth power of T would not yield the information about climate chnage that is sought. As spectrography clearly shows, what is emitted by the Earth to space is not a simple Planck curve; the OLR spectrum diverges very strongly in many bands. The Stefan-Boltzman equation, relating the fourth power of temperature to radiation, cannot be realistically applied universally.
sky
I meant to say “far exceeding in their magnitude the … NET power flux.”
Leif Svalgaard;
There have been such proposals, but they have come to naught.
>>>>>>>>>>>>>>>>
Aw c’mon Leif. Can’t you turn yours around every so often and take a snap of the earth? Do you have to be looking at the sun all the time?
“”””””…..Eliza says:
August 14, 2013 at 2:52 pm
Measuring temperature on Earths surface is only relevant during sunlight hours (clouds or not). If the Earth did not rotate the dark side would be -473K and the other side who knows 2000C? or more? The warmness during night is due to the days exposure to the Sun. Or you could say what would happen to the Earths temperature if the Sun dissappeared? The whole surface would be -473K (temperature of Space) stand to be corrected on the exact K figure there. Of course as you dig deeper the temperature will increase due to gravity. This is assuming no atmosphere of course……”””””
One thing we know for certain Eliza, is that there is NO – *****.***** K anywhere in the universe; or anywhere NOT in the universe, for that matter.
Zero K is as cold as it gets. Maybe by itself, it never gets below about 2.7 K .
Latitude, I assume by “dumbest thing I’ve ever seen” you mean the panic and worry over sea ice extent, right?
Perhaps they are just distancing themselves from the current mess that shows no warming, maybe a little cooling depending on how you look at it. This way they can just claim that the heat energy is hidden in some region that no one is actually measuring. Its convenient that if they don’t like what they find they can just say its meaningless and convince us all to go the Italian way and install solar till were broke. Just a thought, perhaps I am too suspicious.
Steven Mosher says:
August 14, 2013 at 2:45 pm: “…but life is not burger king and you cant have it your way…” Sure we can. We quit funding GISS, CRU and all the other modeling/manipulating psuedo-scientists, and put NASA back to building and (hopefully) launching the IR monitoring satellites (and incoming irradiation) and see what our black body or grey body planet says its energy balance and temperature is.
This SAT is sort of a perverted take on estimating the mineral grade of, say, a porphyry copper deposit. With enough drill holes and assays, a geostatistician can estimate the tenor of the copper mineralization quite well. If he doesn’t, he gets fired, and the mining enterprise built on his estimations possibly fails. Not so, unfortunately, with the lying weasels who are “estimating” the earth’s “temperature”.
Well, I find myself in the curious position of defending Gavin Schmidt against some of the accusations. Let me say that I think Gavin’s science is generally strong, but he’s drunk the koolaid and believes that global temperature is a linear function of the forcing. My main objection is to his censorious ways over at RealClimate, where inconvenient posts never see the light of day.
However, I think he’s getting a bum rap here.
First, there is an assumption that this is a new posting, which is somehow “backing away” from previous certainty. In fact, this is a very old posting, one that I would guess has been there for pushing a decade. I’m sure some genius lurker could tell us when it was first posted, but I assure you it’s been some years.
So everyone ascribing this to bad faith on Gavin’s, or to a climbdown, sorry, you’re wrong. In addition, it highlights the impropriety of ascribing motive in a scientific discussion.
And yes, the concept has been elusive for that long, and remains elusive, for a simple reason.
Temperature is an intensive property of matter.
This means it’s not a function of the amount of matter involved. Mass, on the other hand, is an extensive property of matter. If I have ten one-cm steel ball bearings, and add ten more identical bearings, I’ve doubled the mass … but the temperature hasn’t doubled, has it? Mass is extensive. Temperature is intensive.
Now, in theory you can get a meaningful average of an intensive property, but you’re wandering into uncharted territory. Color, for example, is an intensive property. We can define the pure color by frequency … so what meaning should we assign to the average of 3 blue balls, 2 yellow balls, and 1 red ball? Should we average light, or average pigment? Immediately, we have options.
The problem with averaging intensive measurements is that there are no rules, no “right way” to do it. Suppose we want the average temperature of the globe. We can take all the temperature records and average them … but how do we average them? A huge problem is that the Northern Hemisphere is way over-represented with many more stations, and there are few stations in the Southern Hemisphere.
The way the HadCRUT folks handle it to avoid over-weighting the NH is by first averaging the two hemispheres separately, and subsequently averaging the two hemispheres to give a global value. Is this the right way?
That’s the bad news. There is no “right way” to average an intensive property, particularly in the face of inadequate observations. Determining an extensive property is easy—weigh it, you’ve got the mass. But an intensive property? More observations help, but nothing is final. Some small unmeasured area might be really cold, and there goes your “average” …
There is a deeper problem, which is in the concept of “average” itself. There is a physical meaning to an average of an extensive property. Suppose we have four people who have 2, 3, 6, and 9 pennies respectively. The value of the coins is an extensive property—as the number of coins increases, the value increases proportionately.
Figuring out the average takes two steps. First, we add up the individual contributions to give us the total of the variable, which in this case is 16 pennies. This total has a real physical meaning, it is the count of actual pennies. We can see this by having them pile up all their pennies in the middle.
Then we divide that physical pile by the number of people, four, to give us an average of five cents per person. That has a real physical average.
Now, replace the coins with glasses of water at 2°C, 3°C, 6°C, and 9°C. What is the average temperature of the water? Well, first we add up the temperatures, and we say that the total temperature of the four glasses is 20°C … wait, “total temperature”? Say what?
“Total mass” has a real physical meaning. As a result, “average mass” also has a real physical meaning.
However, “total temperature” has no real physical meaning. It is an artificial construct. As a result, “average temperature” also has no real physical meaning.
There is a final issue, that of “radiation temperature”. For many climate questions the relevant metric is not the temperature, but the corresponding Stefan-Boltzmann energy radiated at that temperature. The issue there is that temperature is not conserved, but energy is. So at times, averaging temperature gives an incorrect answer for the purposes at hand, and what should be averaged is watts per square metre of radiated energy. Once that is averaged, of course, the same equations can transform that amount of radiated energy to the corresponding temperature.
So is that the right way to average temperature? See the answer above. There is no right way, there are different ways. Each one has advantages and disadvantages. None can be said to be the “true” absolute average temperature of the globe.
Which is why Gavin was right to describe the absolute air temperature as being “elusive” … and sadly, while using the temperature anomaly helps, it has its costs as well as benefits. I’m not saying we can’t use it.
I’m just saying that temperature is a difficult metric, that there are judgement calls at every turn, there is no “right way” to do it, and that solidity is elusive on all sides.
There are things you can bust Gavin for. This isn’t one of them.
All the best to everyone, including Gavin,
w.
The Earth abounds with meaningful climate measurements. Coral mounts show sea level was almost 9.5 meters higher 125,000 years ago during the Eemian interglacial; global temperature would be about 6 degrees Celsius higher. Coral mounts dated to 1600 to 8000 years ago indicate sea level three meters higher; roughly 2 to 3 degrees Celsius warmer. Similarly, tree lines were farther north and at higher altitudes during these previous warmer periods, and glaciers had retreated more than present. These natural signs of climate change have import that make the current attempts to measure and extrapolate temperature trends resemble reading the entrails of rabbits to foresee the future. However, in the latter instance you could at least be sure you would have rabbit for dinner; with the current methodology using instruments concentrated in portions of the 30% of the Earth’s surface, and massaged to achieve “homogeneity”, covering a very short time period, all you can be assured of is what you think you are having is not what you get. But that won’t stop the enthusiasts from telling everyone how meaningful whatever it was is, and what it means. At a 95% confidence level.
@rgbatduke
Shouldn’t the emissivity of a particular area, at a particular time be within the inner integral?
Emissivity is a surface property that varies over time, especially in vegetated areas. Doing so, provides for (changing) land use as well as natural effects like seasonal vegetation change, erosion, droughts, …
OMG a proper scientific discussion in the comments … lets keep it up.
Leif Svalgaard says:
August 14, 2013 at 11:10 am
One way of getting at a climate-significant temperature is to measure from a satellite far away in space the amount of radiation [Earth Total Irradiance if you will] received from the Earth [by ‘staring at the Earth’]. From that, an ‘effective’ temperature can be calculated and its variation monitored. There have been such proposals, but they have come to naught.
I agree that is the obvious point to measure and you can baseline it against solar irradiance hitting the satellite … the cost of such a satellite is hardly massive why has no one done it surely can’t be a cost basis given how much is being spent on climate science?
CodeTech says:
August 14, 2013 at 5:14 pm
Latitude, I assume by “dumbest thing I’ve ever seen” you mean the panic and worry over sea ice extent, right?
======
yep you’re spot on as usual…..who decided floating ice was an indication of anything but wind
Willis says:
“First, there is an assumption that this is a new posting, which is somehow “backing away” from previous certainty. In fact, this is a very old posting, one that I would guess has been there for pushing a decade. I’m sure some genius lurker could tell us when it was first posted, but I assure you it’s been some years.”
Indeed so. It’s a page that I have frequently cited over the years here as a reason why it is essential to use anomalies. Here, for example, in 2010.
The NOAA has a similar page.
“I think Gavin’s science is generally strong”
Really? now then i have to ask what you think is science… if someone knows how to count 10 ants and says the result is an elephant that is strong science?
“why it is essential to use anomalies.”
The only reason to use anomalies is to be able to manipulate the results. Nothing more.
Nick Stokes;
Indeed so. It’s a page that I have frequently cited over the years here as a reason why it is essential to use anomalies.
>>>>>>>>>>>>
And, as I have pointed out repeatedly, there is absolutely no physical justification for the use of anomalies, and plenty of reason NOT to. An anomaly of 1.0 at -40C is equal to 2.9 w/m2. An anomaly of 1.0 at +40C is equal to 7.0 w/m2. The notion of anomalies in cold regimes being averaged with anomalies from warm regimes is absurd.
majormike1 says:
August 14, 2013 at 6:15 pm
“The Earth abounds with meaningful climate measurements. Coral mounts show sea level was almost 9.5 meters higher 125,000 years ago during the Eemian interglacial; global temperature would be about 6 degrees Celsius higher. Coral mounts dated to 1600 to 8000 years ago indicate sea level three meters higher; roughly 2 to 3 degrees Celsius warmer.”
A very nice point. I remarked on a sea level discussion associated with Greenland melt not long ago and made the point that along the N shore of Dominican Republic there is coral off shore and the shore itself is pretty much all coral rock (I estimated IIRC it to rise about 6-7m) and the most startling feature was a flat bench cut in the coral all along the coast that is (I thought) 2m above present sea level indicating a former level. You have filled in the blanks for me. It turns my thinking to the idea that sea level alone is about the best we can hope for as a measure of where we are in the climate range. Recent spin papers that dispute the higher temp of the Eemian and optima of the Holocene on the basis of badly designed surveys of calcareous fossils and their oxygen isotope ratios tend to ignore the hard evidence that is sticking in their faces. On the subject of oxygen isotopes in limestones and shells. It is well known by geologists that calcareous deposits tend to become dolomitized and this means that MgO (which abounds in seawater replaces CaO in CaCO3. Are the oxygen isotopes unchanged? In the process is there a preference for which isotopes might stay and which might go with a sea of a different temperature and isotopic composition than the earlier seawater? Is their a biochemist in the house? Anyway, the error bars on their stuff makes for a lot of controversy but solid sealevel changes are pretty good global sentinels of prehistoric climate.
I guessed Gavin Schmidt had written what I thought a well constructed and well balanced piece. When I found it had originated at GISS I wondered if Gavin really had written it. Does anyone know?
Mosher writes:
“Think of it this way
you have a pool. the thermometer at one end reads 74F. the other end reads 76F”
Really, Mosher, your analogy to the earth’s temperature is the temperature of a pool? Do you not realize that using a pool begs all the questions? Your analogy assumes that everything is quite stable, uniform, and, most important of all, all factors are knowable.
How about you try the same explanation with an example that has a little life in it, as the earth does? Take a good sized marsh of the sort that you might drive through on some interstate in Florida. It would be maybe five miles by five miles. How well does your technique work for water temperature in such a marsh?
Steven Mosher says: August 14, 2013 at 2:45 pm
“…it just is what it is. A number that give us a glimpse into a complex system….”
A glimpse it is, but that glimpse is not unimportant in this debate.
In fact, surely it is that ‘glimpse’ and opinion as to its significance, or not, that is behind the formation of the IPCC, climate policies and the ‘green push’ for power and influence, publication of thousands of papers and the creation of thousands of blogs…
….. and the main reason we discuss these issues here with such feeling.
As Willis writes, temperature is an intensive property.
Thus there exists no such thing as an average temperature in a heterogeneous system such as the earth’s atmosphere. It’s already difficult to measure it accurately in a well agitated vessel.
This is why the concept of temperature anomalies was developed: accuracy is no more needed, but reproducibility over time must be given.
In the GISS Q&A I’m missing the question about altitude of the land stations: it cannot be that an average surface temperature will be calculated between measurements made e.g. in Miami and Denver; that value will be meaningless.
Michel:
You end your post at August 15, 2013 at 12:48 am
http://wattsupwiththat.com/2013/08/14/the-elusive-absolute-surface-air-temperature-sat/#comment-1390577
saying
Actually, it is worse than that. All the indications of average global temperature are meaningless.
There are different teams (e.g. GISS and HadCRU) who compute “average global temperature” data sets. Each of the teams uses a different method (i.e. different selection of measurement sites, different weightings to measurements from individual sites, different interpolation methods for values between sites, etc.).
So, the indicated “average global temperature” provided by each team is a unique parameter.
The data sets provided by the various teams are often presented on the same graph (e.g. by IPCC) under the same heading, and there has been no public objection to this by any of these teams. This suggests the teams agree “average global temperature” is a physical parameter that indicates a unique value for the average temperature of the air near the surface of the Earth for each year.
However, the data sets provided by the teams differ such that it is clear they are not indicating the same thing.
The data sets have significantly different trends, and in each of several pairs of years the annual change to “average global temperature” differs between the data sets by more than double the calculated 95% confidence limits of each data set. So, whatever the data sets are indicating, it is apparent that they are not indicating the same thing.
In itself this is not a problem because any data set can have several averages; e.g. its mean, its median, its mode, etc.. However, each of those averages has a specific and defined meaning.
But the “average global temperature” provided by each team is not defined and the method of its calculation is frequently changed; see
http://jonova.s3.amazonaws.com/graphs/giss/hansen-giss-1940-1980.gif
If the teams are each monitoring different climate effects then each should provide a unique title for their data set that is indicative of what is being monitored. Also, each team should state explicitly what its data set of “average global temperature” purports to be monitoring. In the absence of such statements all the indications of “average global temperature” are – both literally and practically – meaningless.
A more full explanation of these issues is provided by Appendix B of the item at
http://www.publications.parliament.uk/pa/cm200910/cmselect/cmsctech/memo/climatedata/uc0102.htm
Richard