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Discussion > I'll bet not a lot of people know this

To get back to the original topic, I have never managed to track down how that actual 'global average temperature' (or whatever it is called) is actually computed from the measured SATs. (EM has stated that it is computed to an accuracy of ±0.1 °C.) I would make a guess that it is some sort of weighted average of the SAT measurements.

Can anyone help me out there?

Apr 12, 2016 at 6:43 PM | Registered CommenterMartin A

ATTP "... how our climate will respond to increasing anthropogenic forcings is not going to depend on whether or not the behaviour of some scientists was not what you would have expected"

Quite true. But (surely?) an equally important point is how our society responds now to the threat of increasing anthropogenic forcings? In that debate, how the participants behave IS likely to affect the outcome. So those who wish to influence others should treat them at all times with the utmost courtesy and respect.

Apr 12, 2016 at 7:06 PM | Unregistered Commenterosseo

As usual, as with Mike Jackson, I find myself in agreement with most of what TBYJ says.

As usual, I find myself balking at much of what aTTP says: “anthropogenically-driven warming” being one good example. The phrase is uttered as if there could be no other explanation for the warming, utterly ignoring the simple fact that this sort of situation has occurred many times in the past, without any influence by humans, at all. Why can it not be happening again? What will be the argument should temperatures drop, as if off the edge of a cliff? (Records do show that that is often what happens should temperatures begin to fall; they fall dramatically.)

Then there is the GHG (greenhouse gas) idea raised: can you be so sure that this is the cause? There are other theories about atmospheres and surface temperatures, theories that look to be more closely verified by observations on other planets than the “greenhouse effect” (GHE) theory is. Why are these dismissed quite so summarily? Of course, aTTP talks about anthropogenic “forcings” as if there was no argument as to their existence; sorry, Mr Rice, but they are still theoretical. When the argument does not go his way, aTTP falls back on a common defence of his – “You are misrepresenting (or misreading; there is a certain amount of internal variablility) what I am saying!” Sorry, again: if you say it walks like a duck, and quacks like a duck, then it is quite reasonable that we assume that it is the duck you are talking about, not the chicken next to it.

aTTP: the principle hypothesis that you defend so vehemently might well be correct; I doubt there are any on this site who do dismiss it as you dismiss alternative hypotheses. However, this does not give you, or any of those of you ilk, carte blanche to dismiss and vilify other hypotheses, nor to pour scorn on those who are not so fully on the side of “the cause” (a term frequently used by many in the UEA CRU). Whenever I have seen people using the term “denier” I have asked what it is that they consider the “deniers” are denying. I rarely get an answer; few that are offered are coherent, let alone cogent.

Finally: hunter – it does not put you in a good light, making comments such as that. Be a good sport and play the ball, not the player.

Apr 12, 2016 at 7:13 PM | Registered CommenterRadical Rodent

osseo,
My personal view is that it would be nice if everyone treated everyone else with courtesy and respect. I don't always achieve this myself.


In that debate, how the participants behave IS likely to affect the outcome.

Yes, this is probably true.


So those who wish to influence others should treat them at all times with the utmost courtesy and respect.

If someone was indeed trying to influence others (car salesman, for example) then this would seem sensible. Scientists, however, are simply trying to present information. What we choose to do with that information is up to us. We can, of course, ignore it if the scientists don't behave as we might like, but that would still be our responsibility, and our fault, if their information suggested we should do something that we decided not to do. Also, if those scientists are regularly accused of lacking in integrity by some who frequent a certain blog, they may find it hard to treat those people with the utmost courtesy and respect; they are only human ;-)

Apr 12, 2016 at 7:34 PM | Unregistered Commenter...and Then There's Physics

ATTP,
You censor and ban people at your pathetic site..
You are a pedantic blithering hypocrite with no apparent ability for self reflection.

Apr 12, 2016 at 8:11 PM | Unregistered Commenterhunter


Of course, aTTP talks about anthropogenic “forcings” as if there was no argument as to their existence; sorry, Mr Rice, but they are still theoretical.

There is very well established radiative physics that allows us to determine the radiative influence of changing GHG concentrations in the atmosphere. There are measurements from space of changes to the outgoing spectrum that are consistent with this radiative physics. There are measurements on the ground of increases in downwelling longwavelength flux that is also consistent with our understanding of radiative physics. If you think that they're only "theoretical" then you presumably regard a great deal of well established science/physics as just being theoretical.

Apr 12, 2016 at 8:14 PM | Unregistered Commenter...and Then There's Physics


You censor and ban people at your pathetic site..

I certainly moderate strongly and do ban some. What of it? It's my site.


You are a pedantic blithering hypocrite with no apparent ability for self reflection.

Okay, but you claimed I was a bully. What has this got to do with bullying and who have I bullied and how? This is a rhetorical question, obviously.

Apr 12, 2016 at 8:24 PM | Unregistered Commenter...and Then There's Physics

I was trying to get the topic onto information theory. I failed, but i have to say that aTTP did try to address my points, but clearly didn't understand the problems in getting a signal from entropic data. Maybe he missed that class in his undergraduate course, or more realistically maybe he's never heard of Claude Shannon. Anyway I'd like for someone to explain to me why you would expect to get a reliable signal out of a data set that is entropic (30 years average SAT) with another entropic dataset (One year average) when the owners of the datasets say you can't measure them.

I'll leave it there.

Apr 12, 2016 at 10:04 PM | Unregistered Commentergeronimo


Anyway I'd like for someone to explain to me why you would expect to get a reliable signal out of a data set that is entropic (30 years average SAT) with another entropic dataset (One year average) when the owners of the datasets say you can't measure them.

Maybe because they don't have a 30 year average SAT and a one year average SAT. There is only one dataset per station. From that you can determine a 30 year average and then the anomalies.

Apr 12, 2016 at 10:33 PM | Unregistered Commenter...and Then There's Physics

"I certainly moderate strongly and do ban some. What of it? It's my site.
Apr 12, 2016 at 8:24 PM | ...and Then There's Physics"

Rather sums up the attitude of climate scientists, to climate science, and the peer review process aswell, as demonstrated by the faked-up 97% consensus.

Yes aTTP, your site is your site, and you are allowed to do with it what you like. Isn't it fortunate that this site is not run along the same lines, as yours, and climate science? Imagine how outraged you would be if you were shut-out, censored or banned.

Apr 12, 2016 at 10:44 PM | Unregistered Commentergolf charlie

Ken, for someone who has Physics in his moniker you miss a lot of the nuance.

There is very well established radiative physics that allows us to determine the radiative influence of changing GHG concentrations in the atmosphere. There are measurements from space of changes to the outgoing spectrum that are consistent with this radiative physics. There are measurements on the ground of increases in downwelling longwavelength flux that is also consistent with our understanding of radiative physics. If you think that they're only "theoretical" then you presumably regard a great deal of well established science/physics as just being theoretical

Radiative physics help us determine the change in radiation in the atmospheric column and have been measured as such. The changes to outgoing spectra, as in the whole spectra, is harder to measure due to things like clouds and how the water column emits in the IR. It leaves a good bit of wiggle room to balance top of atmosphere emission changes in CO2 emission bands. What we do not have direct evidence of is how a change in the CO2 emission bands causes a change in the surface temperature. Which is what you are implying. It cannot be isolated. To try and get an answer there are some large assumptions, one being that no other process of the atmosphere reacts to the change and that the entire lapse rate and water cycle is fixed. A natural consequence of this idea is a tropical hotspot in the tropopause, which hasn't been measured only speculated at with statistics.

As for down welling radiation I assume you mean clouds and aerosols because due to basic atomic physics CO2 near the surface will only have a very weak effect. That pesky absorption rate and shorter mean free path is at work. Meaning that until we get to sufficiently low atmosphere density the only emission from CO2 is because it is hot not that it drives the heat. Convection and absorption are just too dominant.

The main problem with AGW is that it suffers from the Fallacy of Composition, or that it tries to extrapolate effects and assumes the whole works as the part. Another problem and one that is more fundamental is that when dealing with systems you need to characterise its processes and dynamics on sufficient timescales, not just the one you may live in, in order to start to understand what a change in one part will do. Otherwise you end up attributing changes to the wrong thing.

Apr 13, 2016 at 6:02 AM | Registered CommenterMicky H Corbett


Isn't it fortunate that this site is not run along the same lines, as yours, and climate science?

I don't see why.


Imagine how outraged you would be if you were shut-out, censored or banned.

I couldn't care less.

Apr 13, 2016 at 7:27 AM | Unregistered Commenter...and Then There's Physics

Maybe because they don't have a 30 year average SAT and a one year average SAT. There is only one dataset per station. From that you can determine a 30 year average and then the anomalies.

We might be getting somewhere, because I don't understand this response, there is clearly something I don't understand.

My understanding of how they calculate the Global Average Temperature Anomaly (GATA) was that in, say 2015, the global average SAT for that year was calculate from the data available in the SAT temperature record which comprises weather stations and presumably the Argo network. That's one dataset's average.

This average temperature is then compared with the thirty year average, say between 1971 and 2000, that's the average temperature gathered from the weather stations and ocean temperature measurements over that period. You will note another possible cause of entropy in that the sea surface temperatures were previously measured with buckets from ships, so we're not comparing like with like. So that's a second data set of the thirty year average global temperatures.

The 2016 average temperature is then compared to the thirty year average of the thirty year average temperatures and an anomaly calculate, from which we get the GISS, HadCRUT, graphs of temperature anomalies, and "highest ever" temperatures of 0.02C above the previous highest, say 1998, which was itself measured with different instrumentation.

Looking at the Q and A above, and using a modicum of common sense, I can't see how anything remotely reliable can come from this process.

Let me try a simple example. Let's say we have 5000 instruments capable of measuring the temperatures over land and sea. We make an algorithm that takes the min and max daily temperature and decide we'll add them together to divide by 2 and call that the "average" temperature at that location. We then adjust the temperatures to take into account the location of the instruments, altitude, UHI etc., and known defects.

We then use this same network for 30 years to decide the 30 year global average temperature.

The assumption is that the instruments remain precisely the same and in the same locations. At the end of the 30 year period we start to calculate the annual global average temperature using the same instruments and algorithms, and compare this temperature to the 30 year average to get a GATA.

The likelihood is there will be a reasonable signal in that data.

The real world is, of course, a lot messier than that, in fact it's a lot more than a lot messier than that, as we can see above, so why are the scientific community sure that the temperatures they're publishing have any signal worthy of note in them.

To make it clear, I'm dealing only with the issue of the seeming confidence the scientific community in data, which to a layman, looks decidedly dodgy, not with any conspiracies, or accusations of malpractice, I'm assuming good faith from all parties. Furthermore, I'm not challenging the fact that the Earth has warmed. It's solely to do with the confidence the scientific community, from which you'd expect a more trenchant view on accuracy than your average layman, or woman has in the temperature data they putting into policy decisions.

If I have the process wrong I'd appreciate being corrected.

Apr 13, 2016 at 8:03 AM | Unregistered Commentergeronimo

Okay, I think it's not quite as you say. You don't use all the data to produce a single 30-year average, and then use that to determine the anomalies. The anomalies are calculated with respect to the 30 year average for each station and at each time. For example, you have monthly data for 5000 stations. You calculate a 30 year average (over some base period) for each station and for each month. You then compute the anomaly for each station for each month. In other words, the anomaly for Feb 2015 for a particular station is the difference between the Feb 2015 value at that station, and the 30 year average for that station for February. You then average these anomaly values to get the overall anomaly. It's, of course, a bit more complicated than that, but I think that is the general idea.

Apr 13, 2016 at 9:09 AM | Unregistered Commenter...and Then There's Physics

Wow, Mr Corbett (Apr 13, 2016 at 6:02 AM)! You have managed to encapsulate magnificently in so few words what I have singularly failed to do in so many.

Respect!

Apr 13, 2016 at 9:54 AM | Registered CommenterRadical Rodent

… a bit more complicated than that…
A statement that I doubt anyone will disagree with. Have a look at Jennifer Marohasy’s site, and note in her opening statement:

1. Belief in the truth of a theory is inversely proportional to the precision of the science.
“2. The creativity of a scientist is directly proportional to how much [s]he knows, and inversely proportional to how much [s]he believes.

Delve a bit deeper, and see her rail against “homogenisation" of temperatures, a process which seems to increase more recent readings, and decrease more historical ones. Colour me stupid, but that seems to more or less guarantee rising temperatures – even in Uruguay (or is it Paraguay?), where the raw data showed a declining temperature, but the “homogenised” data now shows that it is rising. Woohoo! (Perhaps this might help you understand the cynicism extant amongst many of the sceptics?)

Apr 13, 2016 at 10:20 AM | Registered CommenterRadical Rodent

"Isn't it fortunate that this site is not run along the same lines, as yours, and climate science? 

I don't see why.


Imagine how outraged you would be if you were shut-out, censored or banned.

I couldn't care less.

Apr 13, 2016 at 7:27 AM | ...and Then There's Physics"

People have been driven out of academic environments for those sort of views, but you are immune because of your Green connections. What a supreme display of arrogance.

Apr 13, 2016 at 10:48 AM | Unregistered Commentergolf charlie

What a bizarre response.


People have been driven out of academic environments for those sort of views,

Huh? What's this got to do about academic environments. I'm talking about how I choose to run my blog and how others choose to run theirs. Also, if any of my colleagues conducted themselves in a manner comparable to how some conduct themselves here, I doubt they would do so without being encouraged to stop behaving that way. Academic freedom doesn't quite mean "say whatever you want, whenever you want, wherever you want".


but you are immune because of your Green connections.

Maybe you can tell me what Green connections I have. I'm not aware of any.


What a supreme display of arrogance.

Again, I'm talking about how I run my blog and how others can run their's. If you think it's argument to somehow decide to run something that is yours, you've got a strange view of arrogance. I might even argue that it's rather arrogant of you to think that you can tell me how I should be running my blog.

Lets be clear about something. I've had comments deleted here. I've had most of my comments deleted on Kevin Marshall's site (despite them being on posts in which I'm mentioned) and may be effectively banned. Tom Fuller has banned me and deleted all my comments on the post in which he did so, despite me being mentioned in that post. Paul Homewood recently failed to post my response to his comment and appears to suggest that I can't comment there until I satisfy some condition that he has set.

I'm not complaining; they can run their sites as they wish. However, maybe you should consider that your pearl clutching about how I run my site is based more on my willingness to admit how I do it, than because what I do is somehow wildly different to what is done on sites that probably promote views with which you agree.

Apr 13, 2016 at 11:02 AM | Unregistered Commenter...and Then There's Physics

RR
It may be that there are valid reasons for "smearing" the Paraguay temperatures but we will never know because nobody is prepared to explain why they do these things. That arrogance, which I referred to before, also explains the cynicism you refer to among sceptics.
My far from unique rule of thumb is that where you don't have data then you don't have data. "Oh, it's quite OK to interpolate data up to 1200 miles away. Trust me; I'm a climate scientist" doesn't quite hack it, I'm afraid.
'What you don't know you don't know' and combined with 'you don't know what it is you don't know' half the time makes for an awful lot of guesswork no matter how you dress it up with fancy names.
And an "anomaly" (while we're at it) is defined as 'an irregularity; a deviation from the rule'. There is nothing 'irregular' about a variation of 0.5° from a 30-year average, especially if you understand the meaning of the word 'average'!

Apr 13, 2016 at 11:11 AM | Registered CommenterMike Jackson

My far from unique rule of thumb is that where you don't have data then you don't have data. "Oh, it's quite OK to interpolate data up to 1200 miles away. Trust me; I'm a climate scientist" doesn't quite hack it, I'm afraid.

Sparse coverage is a fact of life in some parts of the world; what do you do for the purpose of calculating an average for areas where there are no thermometers? If you simply miss out the area, you are effectively infilling with the average for the dataset, which may be inacurate say in the Arctic, where temperatures for the region are rising faster han the global average, or you can choose to infill with a value, say the regional or hemispheric value, which will give another answer, or you can extrapolate form the nearest known values. Each choice is defensible and each of the published surface estimates does this slightly differently, which may account for some of the (minor) differences between them.

Do you refer to the 1200 km distance that GISTEMP use when calculating trends? If so, it is described on the GISTEMP website and in a peer-reviewed paper detailed there.

Thought experiment: Take 2 stations on the same site. The temperature rises by 0.1C over a period. Clearly they should both register the same delta-T. Now move one away by a given distance, they will now probably observe a different but still correlated delta-T. Now move it again, and measure the correlation.

What Hansen et al found, by an analysis of the station data, is that the correlation drops to 50% at a distance of 1200 km, and so they chose this as a threshold when extrapolating across sparsely-covered regions. Note that it is temperature change, not absolute temperatures that were found to correlate across distance. [Clearly, that's a simplification, but it captures the gist, read the paper for the detail].

Hansen, J.E., and S. Lebedeff, 1987: Global trends of measured surface air temperature. J. Geophys. Res., 92, 13345-13372, doi:10.1029/JD092iD11p13345.

You're welcome.

Apr 13, 2016 at 1:04 PM | Unregistered CommenterPhil Clarke

…what do you do for the purpose of calculating an average for areas where there are no thermometers?
erm… you don’t? If you don’t have data, you don’t have data; what is it about that simple statement that you do not understand? If you do not have the data, you cannot claim any form of scientific honesty by making data up, which is basically what you are proposing; that is the equivalent of old-time cartographers putting, “Here be dragons,” on those areas they had not surveyed.

Apr 13, 2016 at 2:16 PM | Registered CommenterRadical Rodent

RR,


If you don’t have data, you don’t have data; what is it about that simple statement that you do not understand?

It's not that people don't understand it, it's that it's silly. Extrapolating into areas without data is standard practice and almost always unavoidable. What - in your view - is the minimum area a thermometer should cover before it's acceptable to produce some kind of global temperature anomaly? Or, what is the minimum number of thermometers necessary to do so. There is an actual answer to this, I think.

Apr 13, 2016 at 2:19 PM | Unregistered Commenter...and Then There's Physics

Or, what is the minimum number of thermometers necessary to do so. There is an actual answer to this, I think

Sixty.

To repeat, if you're calculating a global average and you have areas of 'missing' coverage than you either give up and go home or calculate the average with the data you have, which effectively means you're assuming the missing region is at the average for the globe. That's one choice - there are others.

Apr 13, 2016 at 2:35 PM | Unregistered CommenterPhil Clarke

Thanks. I thought it was about 100. We'll see if RR agrees? ;-)

Apr 13, 2016 at 2:44 PM | Unregistered Commenter...and Then There's Physics

Sixty per hemisphere would be ample.

http://journals.ametsoc.org/doi/full/10.1175/1520-0442(1999)012%3C1280%3AEOSDOF%3E2.0.CO%3B2

Either way, the dataset is massively oversampled.

Apr 13, 2016 at 2:50 PM | Unregistered CommenterPhil Clarke