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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I’ve always had a sneaking suspicion that Gavin is the token Real Scientist on the alarmist side.
Is this a new page?
If so, it might suggest Reto has had a hand in it, now Homer’s gone.
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.
So a few tenth’s of a degree are not remotely important and we’ve added only ~0.7 since the 19th Century
With all the uncertainties, it certainly makes a case for satellite based data collection – at least it is an objective way to collect data that is more easily standardized.
…. maybe that’s why NASA GISS is the source – satellites would be right up their alley
According to Vincent Gray, at least the first few question/answers are due to James Hansen. Yes, that James Hansen.
this should not be news to anyone who understands what we mean by SAT
Gary Pearse says:
August 14, 2013 at 11:13 am
So a few tenth’s of a degree are not remotely important
############
settled that science huh?
selective skepticism is funny
selective skepticism is funny
bedwetting is even funnier
Don’t tell me there’s a chance they might actually return to doing science.
It appears to me that the only absolute temperature that would have any relevance would be from the temperature readings at Mauna Loa, since this seems to be the only relevant place on the earth that CO2 readings are taken. This, of course, begs the question: Why do not weather forecasts include local CO2 readings if levels of atmospheric CO2 have an impact upon climate? What impacts weather also impacts climate. Right?
Great article Anthony – in real life we all know walking around you hit warmer and cooler patches everyday even on level ground. I have said the same forever – there is no common temperature for anyplace at anytime. Land height, wind direction, moisture content, cloud cover, sun, shade, buildings, rock, sand, vegetation, etc. all play a part with so many temperatures at any given location no computer program is capable of duplicating.
After all the discussion about the impossibility of measuring or even defining the SAT, the last paragraph says it is 57.2 +- 1 degree F. Which translates to 287 K +- 0.55 K, an error of about 0.2%! Would that other climate parameters could be measured so precisely.
“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…”
–
The difference between 57.2 and 56 is 1.2 degrees F. Isn’t that about how much the planet has supposedly warmed over the past century? So, basically this is an admission that the estimated amount of modern global warming falls within the margin of error for measuring global mean temperature. Doesn’t that make it statistically indistinguishable from zero? If so, that’s quite an admission.
One of my criticisms of climate models is that they produce very different values for global temperature when expressed as absolute values rather than anomalies. Typically a ‘warm’ model simulates temperatures that are 1.5 °C higher than a ‘cool’ model.
http://www.climatedata.info/Temperature/Temperature/simulations.html
Steven Mosher says:
August 14, 2013 at 11:23 am
this should not be news to anyone who understands what we mean by SAT
Gavin says:
Q. What exactly do we mean by SAT ?
A. I doubt that there is a general agreement how to answer this question.
Perhaps Mosher could fill us all in (including Gavin) on “what we mean by SAT”
“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.”
Wow. The slow, dissembling backing away from alarmism?
Leif Svalgaard says:
August 14, 2013 at 11:10 am
…There have been such proposals, but they have come to naught.
Ummm…they don’t want actual measurements…empirical data would ruin their scam!
“…let the model run long enough so that the initial guesses no longer matter,…”
I think a little detail is omitted in this statement…if the initial guess no longer matter, then you should not need them at all, and I’m sure that’s not what they meant to say.
Lance Wallace
“What we mean by SAT” is a vague attempt to define a nearly meaningless concept. Does that help any?
Louis says:
August 14, 2013 at 11:47 am
=======
yep
“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.”
Number one: the question was not answered.
Number two: “exactly what you need” for what? For time series analysis? Can we never escape the church of time series analysis and travel to the land of actual physical science? Anomalies are faux data produced through human contrivance to make time series analysis easier. No actual physical theory takes such human contrivance as data. Actual thermometer readings will serve as the only data for climate science once it becomes a genuine physical science.
Gary Pearse, I always have to remind myself that we are talking a range of less than a degree Celsius between the warmest and coldest year on record… Its a grand debate of tenths,
JimS says:
August 14, 2013 at 11:32 am
Part of the gospel of Alarmism is that CO2 is well mixed in the atmosphere. Ask them how it gets from its major sources to Mauna Loa and you will get no answer. Apparently, they believe that all of it travels straight up for 20 miles or so and then travels laterally and sinks.
Oh, how I would like to find everyone warmist I’ve ever “debated” and put this in front of them. Something I’ve been arguing with them for years.
“What is the temperature of the earth right now”?, I would ask, knowing that there is no answer.
“Scientists say…” they would begin.
“No, some scientists say X, some say Y, some say Z”, I would correct.
“You’re an uneducated turnip”, they would parry.
“You don’t know the temperature of the earth now, you can’t tell me what the temperature of the earth was yesterday, last year or 10,000 years ago, and can’t tell with any reasonable degree of certainty what it will be like in years, decades or centuries because the scientists don’t know themselves”, I would counter.
“You’re just regurgitating oil-industry propaganda from an un-peer reviewed source” would be the reply.
“NASA isn’t a good source?”, I would inquire, nicely.
“This blog says…” would come the retort.
“Did you just quote an un-peer reviewed blog to counter a NASA statement?”, I pointed out, helpfully.
“Your grandchildren will hate you!!!!”, or words to that effect.
Or, worse, they would counter with another NASA webpage that contradicted the one I posted, the irony of their proving my point for me not even slowing them down…
Thank you, Anthony.
There is no easy way to measure the temperature in that it is measured in a consistent manner through out time.