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Are surface temperature records reliable?

What the science says...

Select a level... Basic Intermediate Advanced

The warming trend is the same in rural and urban areas, measured by thermometers and satellites, and by natural thermometers.

Climate Myth...

Temp record is unreliable

"We found [U.S. weather] stations located next to the exhaust fans of air conditioning units, surrounded by asphalt parking lots and roads, on blistering-hot rooftops, and near sidewalks and buildings that absorb and radiate heat. We found 68 stations located at wastewater treatment plants, where the process of waste digestion causes temperatures to be higher than in surrounding areas.

In fact, we found that 89 percent of the stations – nearly 9 of every 10 – fail to meet the National Weather Service’s own siting requirements that stations must be 30 meters (about 100 feet) or more away from an artificial heating or radiating/reflecting heat source." (Watts 2009)

At a glance

It's important to understand one thing above all: the vast majority of climate change denialism does not occur in the world of science, but on the internet. Specifically in the blog-world: anyone can blog or have a social media account and say whatever they want to say. And they do. We all saw plenty of that during the Covid-19 pandemic, seemingly offering an open invitation to step up and proclaim, "I know better than all those scientists!"

A few years ago in the USA, an online project was launched with its participants taking photos of some American weather stations. The idea behind it was to draw attention to stations thought to be badly-sited for the purpose of recording temperature. The logic behind this, they thought, was that if temperature records from a number of U.S. sites could be discredited, then global warming could be declared a hoax. Never mind that the U.S. is a relatively small portion of the Earth;s surface. And what about all the other indicators pointing firmly at warming? Huge reductions in sea ice, poleward migrations of many species, retreating glaciers, rising seas - that sort of thing. None of these things apparently mattered if part of the picture could be shown to be flawed.

But they forgot one thing. Professional climate scientists already knew a great deal about things that can cause outliers in temperature datasets. One example will suffice. When compiling temperature records, NASA's Goddard Institute for Space Studies goes to great pains to remove any possible influence from things like the urban heat island effect. That effect describes the fact that densely built-up parts of cities are likely to be a bit warmer due to all of that human activity.

How they do this is to take the urban temperature trends and compare them to the rural trends of the surrounding countryside. They then adjust the urban trend so it matches the rural trend – thereby removing that urban effect. This is not 'tampering' with data: it's a tried and tested method of removing local outliers from regional trends to get more realistic results.

As this methodology was being developed, some findings were surprising at first glance. Often, excess urban warming was small in amount. Even more surprisingly, a significant number of urban trends were cooler relative to their country surroundings. But that's because weather stations are often sited in relatively cool areas within a city, such as parks.

Finally, there have been independent analyses of global temperature datasets that had very similar results to NASA. 'Berkeley Earth Surface Temperatures' study (BEST) is a well-known example and was carried out at the University of California, starting in 2010. The physicist who initiated that study was formerly a climate change skeptic. Not so much now!

Please use this form to provide feedback about this new "At a glance" section, which was updated on May 27, 2023 to improve its readability. Read a more technical version below or dig deeper via the tabs above!

Further details

Temperature data are essential for predicting the weather and recording climate trends. So organisations like the U.S. National Weather Service, and indeed every national weather service around the world, require temperatures to be measured as accurately as possible. To understand climate change we also need to be sure we can trust historical measurements.

Surface temperature measurements are collected from more than 30,000 stations around the world (Rennie et al. 2014). About 7000 of these have long, consistent monthly records. As technology gets better, stations are updated with newer equipment. When equipment is updated or stations are moved, the new data is compared to the old record to be sure measurements are consistent over time.

 GHCN-M stations

Figure 1. Station locations with at least 1 month of data in the monthly Global Historical Climatology Network (GHCN-M). This set of 7280 stations are used in the global land surface databank. (Rennie et al. 2014)

In 2009 allegations were made in the blogosphere that weather stations placed in what some thought to be 'poor' locations could make the temperature record unreliable (and therefore, in certain minds, global warming would be shown to be a flawed concept). Scientists at the National Climatic Data Center took those allegations very seriously. They undertook a careful study of the possible problem and published the results in 2010. The paper, "On the reliability of the U.S. surface temperature record" (Menne et al. 2010), had an interesting conclusion. The temperatures from stations that the self-appointed critics claimed were "poorly sited" actually showed slightly cooler maximum daily temperatures compared to the average.

Around the same time, a physicist who was originally hostile to the concept of anthropogenic global warming, Dr. Richard Muller, decided to do his own temperature analysis. This proposal was loudly cheered in certain sections of the blogosphere where it was assumed the work would, wait for it, disprove global warming.

To undertake the work, Muller organized a group called Berkeley Earth to do an independent study (Berkeley Earth Surface Temperature study or BEST) of the temperature record. They specifically wanted  to answer the question, “is the temperature rise on land improperly affected by the four key biases (station quality, homogenization, urban heat island, and station selection)?" The BEST project had the goal of merging all of the world’s temperature data sets into a common data set. It was a huge challenge.

Their eventual conclusions, after much hard analytical toil, were as follows:

1) The accuracy of the land surface temperature record was confirmed;

2) The BEST study used more data than previous studies but came to essentially the same conclusion;

3) The influence of the urban stations on the global record is very small and, if present at all, is biased on the cool side.

Muller commented: “I was not expecting this, but as a scientist, I feel it is my duty to let the evidence change my mind.” On that, certain parts of the blogosphere went into a state of meltdown. The lesson to be learned from such goings on is, “be careful what you wish for”. Presuming that improving temperature records will remove or significantly lower the global warming signal is not the wisest of things to do.

The BEST conclusions about the urban heat effect were nicely explained by our late colleague, Andy Skuce, in a post here at Skeptical Science in 2011. Figure 2 shows BEST plotted against several other major global temperature datasets. There may be some disagreement between individual datasets, especially towards the start of the record in the 19th Century, but the trends are all unequivocally the same.

rural-urban T

Figure 2. Comparison of spatially gridded minimum temperatures for U.S. Historical Climatology Network (USHCN) data adjusted for time-of-day (TOB) only, and selected for rural or urban neighborhoods after homogenization to remove biases. (Hausfather et al. 2013)

Finally, temperatures measured on land are only one part of understanding the climate. We track many indicators of climate change to get the big picture. All indicators point to the same conclusion: the global temperature is increasing.


See also

Understanding adjustments to temperature dataZeke Hausfather

Explainer: How data adjustments affect global temperature recordsZeke Hausfather

Time-of-observation Bias, John Hartz

Berkeley Earth Surface Temperature Study: “The effect of urban heating on the global trends is nearly negligible,” Andy Skuce

Check original data

All the Berkeley Earth data and analyses are available online at

Plot your own temperature trends with Kevin's calculator.

Or plot the differences with rural, urban, or selected regions with another calculator by Kevin

NASA GISS Surface Temperature Analysis (GISSTEMP) describes how NASA handles the urban heat effect and links to current data.

NOAA Global Historical Climate Network (GHCN) DailyGHCN-Daily contains records from over 100,000 stations in 180 countries and territories.

Last updated on 27 May 2023 by John Mason. View Archives

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Argument Feedback

Please use this form to let us know about suggested updates to this rebuttal.

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Further reading

Denial101x video

Here is a related lecture-video from Denial101x - Making Sense of Climate Science Denial

Additional video from the MOOC

Kevin Cowtan: Heat in the city


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Comments 476 to 500 out of 529:

  1. Tom, I will try to make this simple. The only constant I see is claiming every decade we see a number of the warmest years. It's their MO.

    Hansen published in a peer-reviewed article that 4 of the warmest years on record were in the 80s. I can show you that if you don't believe me. Then when challenged on 1998 being the warmest year, to make a long story short, he moderates and says 1998 was tied with 1934 as the warmest year.

    Wait, what happened to the 4 years in the 80s that were supposedly warmer than 1934?

    At some point, you gotta say this looks like some bigtime bs. The only consistent thing is the scare-mongering and claims a number of the past 10 years are the warmest ever and pretty soon NYC will be under water or some such

    Pretty soon it will be 2018 and none of the predictions will have come true but we will still hear the same based on "adjustments" to the data selling the same narrative.


    [DB]  Multiple instances of off-topic, sloganeering and inflammatory snipped.

    Please note that posting comments here at SkS is a privilege, not a right.  This privilege can and will be rescinded if the posting individual continues to treat adherence to the Comments Policy as optional, rather than the mandatory condition of participating in this online forum.

    Moderating this site is a tiresome chore, particularly when commentators repeatedly submit offensive, off-topic posts or intentionally misleading comments and graphics or simply make things up. We really appreciate people's cooperation in abiding by the Comments Policy, which is largely responsible for the quality of this site.
    Finally, please understand that moderation policies are not open for discussion.  If you find yourself incapable of abiding by these common set of rules that everyone else observes, then a change of venues is in the offing.

    Please take the time to review the policy and ensure future comments are in full compliance with it.  Thanks for your understanding and compliance in this matter, as no further warnings shall be given.

  2. Randman, it appears you have also not read the Nature news article (with its linked scientific paper by Dieng et al, 2017) which demonstrates the opposite of what you said.  A scientific source which you yourself referenced.  Or perhaps you did read that, and chose to brazenly misrepresent the sea level information.

    Randman, your credibility is zero — though you do score points for black humor and/or orange-haired chutzpah in your promotion of Alternative Facts.

    But you go too far, Randman.  For even the Chief of Alternative Facts knows that more ice melts as conditions get warmer.

  3. randman @461.

    I am struggling to keep up with your wild pronouncements.

    You claim that "Hansen's 1981 paper has the mean from 1950-1980 at 288" with a link to Hansen et al (1981) which says no such thing. It does say "The mean surface temperature is Ts ~288K" but this is not associated with any global average temperature measurements or the period 1950-80. Instead, it is presented to illustrate the power of the greenhouse effect on climate.

    And the second piece of evidence you provide is another NYT article, this one from 1988 which tells us "How hot is the world now? The scientists do not offer a straightforward response, saying that the vast amount of data is still being studied and that comparisons cannot be precise." It is in this context that the article offers an average global temperature from Hansen:-

    "One of the scientists, Dr. James E. Hansen of the National Aeronautics and Space Administration's Institute for Space Studies in Manhattan, said he used the 30-year period 1950-1980, when the average global temperature was 59 degrees Fahrenheit, as a base to determine temperature variations."

    I would suggest the 59ºF being quoted in both the 1988 and 1989 NYT articles results from a journalist insisting on obtaining an average temperature to better inform his readers, a value reluctantly provided by his interviewees. It is certainly no indication of any "consensus" and your insistence that there has been a revision of the temperature record remains entirely unfounded.

    May I also correct some of your confusion @476.

    You describe "the 4 years in the 80s that were supposedly warmer than 1934," the four 80s years being "4 of the warmest years on record were in the 80s" apparently set out in a peer-reviewed article by Hansen. Without sight of that article, I note in yet another 1988 NYT article it is stated that "Dr. Hansen ... had previously reported that four of the hottest years on record occurred in the 1980's." So of the years 1980-87, Hansen had reported that four of these years exceeded all pre-1980 anomalies. Where have they gone? A quick glance at GISTEMP LOTI shows they (1987, 81, 83, 80) are still there.

    As for 1934, all 1980s years are warmer than 1934 by some considerable degree. However there has been a bit of a kerfuffle involving 1934 it being for some years (and may still be for all I know) the hottest year on record in the "contiguous states."

  4. randman,

    I don't often comment here, but thought I would this time since I may be able to answer your question on the change in global mean temperature for 1951-1980.

    I suspect that you're mistaken about what paper Hansen used to get that value. I suspect it actually came from  Hansen and Lebedeff, 1987. (There's also an updated version of that paper from 1988, but I can't find a copy of it and it just seems to include the data through 1987, so it probably doesn't change anything.) If you look at Figure 1 in that paper, you'll notice that the paper is missing a lot of data from the oceans. More recent attempts to find global temperatures has included ocean temperatures as well, and I believe that will tend to lower the global temperature values overall. (See also  Victor Venema's blog about station data homogenization. You might read some of the articles on Victor's blog - they may answer some of your questions.)

    I don't think it's particularly surprising to find that, as time moves on, science has found better answers to questions - that is, after all, kind of the point of science. 


    [TD] I fixed the links. You can't type HTML to enter a link. You must click the Insert tab and then the link button. I deleted your followup with the now-redundant links.

  5. randman: You are Gish Galloping. You complained about absolute temperature estimates changing, but you were mixing terms and concepts. Several people gave you information that answered your question and (should have) cleared your confusion.

    Then you were complaining about supposed changes in estimates of temperature changes. Scientists do not measure changes in temperature by differencing one year's absolute global temperature from an earlier year's absolute global temperature. Instead they difference anomalies. After that was explained to you several times you insisted that you fully understood that.

    Now you are complaining about supposed changes in relative temperatures. Again. But you are acting as if you have been discussing the same topic all along, and that I am an idiot for not recognizing that. No. You have been changing topics. Several people have been trying to give you the answers you are asking for, but you are a moving target.

  6. Tom, where have you explained how the consensus mean from 1950-1980 was considered to be 15 degrees celsius and later changed to 14 degrees celsius?

    Nothing you've "explained" explains that. This has signifant ramifications because if the mean was 15 degrees, we've experienced no warming the past 30 years and the whole thing crashes like a house of cards. It'd be like amassing all this evidence someone committed a murder but then the guy supposedly murdered shows up alive. That "evidence" is then moot.

    Now you can talk about comparing changes in individual weather stations and amassing those averages and differences all you want or any other technique but that's a separate question. Could be they changed how they do that? Could be they just arbitrarily lowered everything en-masse? Could be the adjustment to 14 degrees is totally honest and the same standards are applied to recent temperatures as to those such that if we went with the old standards, we'd have global means higher than 15 degrees celsius?

    But where are the peer-reviewed papers discussing why the mean was lowered, which coincidentally makes the past 30 years look warmer relative to that mean?


    [DB] Blatant lies snipped.

    Please note that posting comments here at SkS is a privilege, not a right.  This privilege can and will be rescinded if the posting individual continues to treat adherence to the Comments Policy as optional, rather than the mandatory condition of participating in this online forum.

    Moderating this site is a tiresome chore, particularly when commentators repeatedly submit offensive, off-topic posts or intentionally misleading comments and graphics or simply make things up (i.e., blatantly lie). We really appreciate people's cooperation in abiding by the Comments Policy, which is largely responsible for the quality of this site.
    Finally, please understand that moderation policies are not open for discussion.  If you find yourself incapable of abiding by these common set of rules that everyone else observes, then a change of venues is in the offing.

    Please take the time to review the policy and ensure future comments are in full compliance with it.  Thanks for your understanding and compliance in this matter, as no further warnings shall be given.

  7. Steve, thanks for answering or trying to. Will look at those papers and blog on the oceans. However, not precisely sure estimating past oceanic readings to lower the mean is necessarily valid. At a minimum, it should be a reasonable discussion and debate. We, in the public, are being asked to use governmental power to make wide-raning changes, and yet what appears to me as the answer to reasonable questions is often just to shout people down and call them deniers. Moreover, it really looks very fishy. Bold predictions were made that didn't come true and then the mean in the past is lowered, which coincidentally props up the theory as well as the flow of funding?

    Btw, the reference ot 288 Kelvin is from 1981 but will look at the papers you mentioned as well.


    [PS] Sloganeering removed.

    So far your participation on this forum shows you asking reasonable questions based on a misreading of media reporting, misunderstanding of how temperature series are constructed and now misunderstandings of how and why adjustments are made. Furthermore you "reasonable" questions would seem to suggest that you have uncritically accepted misinformaton from denialist sources. Just because you misunderstand something does not make it wrong.

    If you wish to participate here can I suggest the following:

    A/ Consider the possibility that your understanding of the science may be wrong and misinformed. People here are trying to fix that but it behoves on you to put reasonable effort into understanding the explanation and reading resources provided. Clinging to misinformation because it suits your beliefs is the heart and soul of denial and you dont want to be accused of that do you?

    B/ Cite your sources. Do not make statement without saying what informs your opinion preferably with link or at least a proper cite. Hansen 81 is barely good enough - a title it much better.

    C/ If you wish to claim science is wrong, then first cite the reference where science makes the claim you dispute. (Straw man claims are the heart of denialist blogs). Then cite the evidence which you think disproves the claim. Doing this will get reasonable responses from people here.

    Any further sloganeering will simply result in comments being deleted. The comments policy here is not optional.

  8. Steve, if interested, this the 1981 paper with 288 Kelvin as the 1950-1980 average.



    [RH] Can I request that you learn how to use the embed function for links? Some long links break our page formatting. It's quite easy to create a short description or title and then embed the link into the text. Thx.

  9. Tom, this is the paper by Hansen with 288 Kelvin as the mean. I think you've already seen the press comments by Hansen and Jones in 1988 of 59 degrees F and "roughly 59 degrees" respectively, right? 


    Obviously regardless of looking at anomalies, there is a reason they believed the mean was 59 degrees. The fact climatologists like to look at anomalies does not change that, does it? Not seeing your point.

    On a wider note, this appears to be a pattern. 15 degrees was later adjusted down to 14 degrees, which had the effect of making the then present temps appear warmer, whether correctly so or not. 

    More recently, we've seen satellite data that showed no sea level rise to speak of "adjusted", perhaps correctly so or not, to now show sea level rise.

    Prior to that we saw the posited warming hiatus changed by some, which changes including lowering the past means among other things. One climatologists somewhat famously has complained about this, Judith Curry. Some of her comments here:

    ""This short paper in Science is not adequate to explain and explore the very large changes that have been made to the NOAA data set," she wrote. "The global surface temperature data sets are clearly a moving target. So while I'm sure this latest analysis from NOAA will be regarded as politically useful for the Obama Administration, I don't regard it as a particularly useful contribution to our scientific understanding of what is going on.""

    As I understand it, Curry was a proponent of AGW and perhaps still is in some respect, but has had problems with the way the data has been adjusted and the accuracy of the models among other things.

    She's not the only scientist raises these questions. So it's not just laymen like myself who wonder why there appears to be a pattern of data that does not line up with predictions simply being "adjusted." These adjustments are not just one-off things either but a fairly consistent feature here.


    [DB] Blatant lie snipped.  Sloganeering snipped.

    [PS] "Obviously regardless of looking at anomalies, there is a reason they believed the mean was 59 degrees. "

    And just as obviously, you still have not understood that anomaly measurements do not reference a global absolute temperature. Until you bothered to study and understand this, you cannot make progress. Read the material provided.

    [RH] Shortened link.

  10. These are quotes from this particular site on how to understand calculations of anomalies.

    " The World Meteorological Organisation (WMO) defines Climate as the average of Weather over a 30 year period. So if we look at a location averaged over something like a 30 year period and compare the same location averaged over a different 30 year period, the difference between the two is how much the average temperature for that location has changed. And what we find is that they don’t change by very much at all.
    Rather than averaging all our stations together, instead we start out by looking at each station separately. We calculate its long term average over some suitable reference period. Then we recalculate every reading for that station as a difference from that reference period average. We are comparing every reading from that station against its own long term average. "

    So comparing individual station's data "against its own long term average", which means calculating the long-term, maybe 30 year term average is critical to assessing the difference between measurements against that average.

    Not very complicated. 

    As I stated on other posts, the mean in Hensen's paper for 1950-1980 globally was very close to 15 degrees, and in 1988 he said the mean was 15 degrees and Jones in 1988 said "roughly 15 degrees." Those are facts of what was stated and reported, whether correctly or not.

    Some here have accussed me of not understanding the calculations of anomalies. Of course, individual stations are not compared to the global mean. Some areas are warmer or colder than others, for example. That would be ridiculous.

    However, statements of, for example, the warmest year ever are not based on mere consideration of a single or a few stations but on an aggregate of all the data, which would include either all stations or a sufficient spread of them to make a reasonable calculation.

    It is doubftul Hansen and Jones just made up the number of 59 degrees or 15 degrees celsius. Hope not at least. Hansen was testifying before Congress and arguing global warming was a very serious issue.

    One must assume they based their view of the mean from 1950-1980 on actual data, right? They were looking at changes in the temperature record at each individual station and analyzing that. Since then, we see the global mean surface temp announced with claims of one year being warmer than another and so forth.

    So if based on studying this data, the claim was the mean from 1950-1980 was 15 degrees celsius, can someone please show the peer-reviewed papers justifying lowering it to 14 degrees? Just asking that once again. Only one person has even tried to answer by suggesting some possibilities, linking to a blog to look further, and yet to me, I would think this is something proponents would have on-hand. I mean, of course, there should be an explanation of such a large shift on the view of what the data indicated, right?


    [PS] The whole point of anomaly method is that absolute temperature average is very difficult to measure with any precision (and is dubious as to whether it is meaningful number in any actual application), whereas change in the anomaly can be measured with considerable confidence. Hansen's number of 15 degree is really a rough estimate.

    As far as I can tell, nobody gets where you have inferred that temperature average has somehow been lowered and you seem to implying nefarious adjustment from this. If you understand that trends are change in anomaly from some baseline, then why are going on about absolute temperature? it is meaningless in this context.

  11. In response to the mod, I am merely asking for the peer-reviewed papers that show the adjustment. If you are requiring something stating 14 degrees celsius at present, I an easily do that. If you are saying that's meaningless, c by the way, to compare current global surface temps in claims of the hottest year and so forth, something we see a lot of?

    What's with the press reports stating 2016 was the hottest year, for example, if that's such a dubious claim to begin with? Only way to argue it was the hottest year, as just an example of what I am talking of, is to have an idea what the prior year's were. So if you start saying the mean from 1950-1980 was roughly 15 degrees celsius and then have numerous years you state are less than 15 degrees celsius, obviously you no longer consider the mean from 1950-1980 to be correct, right?

    I am not understanding your grievance here. All I am asking for is how that determination to revise downward the mean happened. Where are the papers showing that? Is your position none are needed?


    [PS] There is no adjustment. We are trying to understand why you think there is one. Where do you get the idea that absolute temperature is now 14 and was 15 in past? In what context do you see absolute temperature being stated and used? You claim a certain year is hottest because the anomaly has changed x degrees from baseline. The baseline defines zero. There is no need to know what that is in absolute terms. Look at the graphs of various temperature series in the article. They never report a temp. Only the change of the average of the anomalies.

    Our "grievance" is struggling to understand how you have your wires so badly crossed about something that is fairly simple. A temperature station doesnt report that average temperature in 2000 is say 17. It reports that is say 0.8 degrees higher than whatever the average of that stations temperatures was from 1950-1980. Spatially average all those differences from all the stations worldwide and you have the number plotted on all those graphs above.


  12. randman, you wrote

    "statements of, for example, the warmest year ever are not based on mere consideration of a single or a few stations but on an aggregate of all the data, which would include either all stations or a sufficient spread of them to make a reasonable calculation."

    Correct. But then you implicitly made an incorrect conceptual leap. You incorrectly assumed that the "aggregate of all the data" is the global mean absolute temperature. It is not. The data being aggregated are the anomalies. Therefore the aggregate of those anomalies is the global mean anomaly temperature. Not the absolute temperature. The absolute temperature for the globe never is calculated in that procedure. Even the absolute temperatures for each of the individual stations disappear from the data as soon as the individual anomalies are calculated.

    Estimating the mean absolute temperature of the globe cannot be done to any useful precision or accuracy simply by averaging the absolute temperatures of all the individual stations. The operations for doing it instead are very complex, require much more information and assumptions, and inevitably yield an estimate that is an order of magnitude (that's 10 times--move the decimal point to the right by one digit) less certain than an estimate of global mean anomaly. Changing any of that can yield a very different global mean absolute temperature even if 100% of the individual absolute temperature measurements are not changed.

    People have been attempting to estimate global mean absolute temperature since at least Fourier's calculation in the 1820s, which allowed him to realize that the atmosphere was insulating the Earth. There have been, and ongoing continue to be, many estimates, and they have and continue to vary between each other, even when they use exactly the same temperature measurements as inputs. So your claim that "the" estimate of the mean global absolute temperature was changed from 15 to 14 degrees Farenheit, is wrong. There never has been a robust consensus on absolute global mean temperature at high precision nor high accuracy. If you really were interested in absolute temperature, you would have surveyed the considerable literature.

    But you did not. Your citation of the Hansen et al. paper for your 15 degree claim is inappropriate. I believe global mean absolute temperature was mentioned in that paper only once, was only approximate ("~288"), and was mentioned only in passing as context for the rudimentary and obligatory background introduction about the laws of radiation and so on. That paper did not in any way address the precise value, and the authors did not in that paper describe any of their work to attempt to determine that value, because that paper instead described only their work to estimate the trend with anomalies. I would be shocked if estimates of absolute temperature have not  changed over the decades, because climatologists have continued to attempt to improve their estimates. But not for the purpose of better estimating the trend of global temperature change.

    The mean absolute temperature of the globe could be re-estimated to be 40 degrees colder or warmer without in any way affecting the mean anomaly of the globe. It's just arithmetic.

    People interested in global warming are interested in the how fast the global mean temperature is increasing. That is the "trend" in the global mean temperature. The trend is the "slope" of the graph of temperature by time. The absolute temperature is irrelevant to the slope; changing it merely slides the curve up and down the y (temperature) axis, leaving the slope unchanged. Literally, unchanged. Because of arithmetic.

  13. randman, you wrote "why is it published and stated and used, by the way, to compare current global surface temps in claims of the hottest year and so forth, something we see a lot of?" You are flatly, objectively, wrong. Absolute temperatures are not used in claims of the hottest year. Relative temperatures (anomalies) are used.

    You wrote "Only way to argue it was the hottest year, as just an example of what I am talking of, is to have an idea what the prior year's were." Yes, you are correct. But the prior year's temperature need not be known as absolute temperature. The temperature relative to any baseline period's temperature is completely, perfectly, logically, mathematically, sufficient, as long as both this year and the prior year's anomalies are calculated from the same baseline time period.

  14. So why would the Washington Post mention an absolute temperature and claim the NOAA does?

    "The average temperature across the world’s land and ocean surfaces was 58.69 Fahrenheit, or 1.69 degrees above the 20th-century average of 57 degrees, NOAA declared. "

    Note it is less than 59 degrees. So obviously if in the 80s people like Hanson and Jones believed the cumulative data indicated 59 degrees as the mean from 1950-1980, then there has been an adjustment in that data such that the NOAA can declare less than 59 degrees the hottest year ever since data has been collected.

    Where is the explanation and peer-reviewed papers discussing that downward revision?

  15. Tom you do realize the slope is pretty easily manipulated based on the time-frame involved among other things, right?

    The bottom line are the comments of 59 degrees as a mean from 1950-1980 were not arbitrary. I am open to explanations from those involved as to why they were wrong. At the same time, adjusting the past temps down, excluding stations, adjusting temps from stations, etc,...make a very big difference in calculating anomalies, right? They are based on a mean of specific weather stations or measurement instruments. 

    So the question is if adjustments are made, why were they made? Are the same standards applied to the present measurements such that there is an honest account of relative changes. Just show the papers and data.

    What's the problem here? You guys have a beef with someone like me watching this unfold for 30 years, hearing the mean was 59 degrees or 15 degrees celsius, and then seeing over and over again that such and such year was the warmest with an announcement of the mean for that year less than 15 degrees celsius?

    Can't you see how any normal person would take that with a grain of salt. At least show me why and how you changed your view of the data in the past.


    [DB] Blatant lie and inflammatory snipped.

  16. Ok, just googled the NOAA and this just an illustration mind you and clicked on first or near thing that came up.

    "Driven by record warmth in the West, the national average summer (June–August) temperature for the contiguous U.S. was 72.7°F, 1.3°F above average and the 15th warmest summer in the 123-year period of record."

    I don't propose there is anything controversial here. Just posting it to point out an absolute average temperature is mentioned here for the US and specified to be the 15th warmest year. 

    Now, I am sure I can look up other announcements from those keeping such records that mention absolute temps. This should not be controversial. It's not out of bounds to talk of things in this manner.

    So why did Hansen and Jones think the mean from 1950-1980 was 15 degrees roughly and yet now it is considered to have been 14 degrees?

  17. "The result of these calculations is an estimate of the global average temperature difference from a baseline period of 1951 to 1980.


    So NASA stated their calculations are "an estimate of the global average temperature difference from a baseline period of 1951 to 1980."

    "Baseline"?  "Global average"?

  18. Ah, now I understand. "Randman" sucked me in to his game. He can't be that stupid. He's just been jerking us around for his own amusement.

  19. Please note the source of this:

    "The basic GISS temperature analysis scheme was defined in the late 1970s by James Hansen when a method of estimating global temperature change was needed for comparison with one-dimensional global climate models. The scheme was based on the finding that the correlation of temperature change was reasonably strong for stations separated by up to 1200 km, especially at middle and high latitudes. This fact proved sufficient to obtain useful estimates for global mean temperature changes.

    Temperature analyses were carried out prior to 1980, notably those of Murray Mitchell, but most covered only 20-90°N latitudes. Our first published results (Hansen et al. 1981) showed that, contrary to impressions from northern latitudes, global cooling after 1940 was small, and there was net global warming of about 0.4°C between the 1880s and 1970s."

    So NASA here points to the same 1981 paper I have brought up, which mentions a mean of 288 Kelvin which is 14.85 degrees celsius. They came up with number somehow. Talking of how the process involves individual stations does not change that. This is on their website. This is what they state.

    Now it is clear that 14.85 degrees celsius or 15 degrees celsius which Hanson mentions 7 years later in 1988 is not still considered valid. Otherwise they wouldn't be saying annual means of less than that are hotter.

    So despite bashing me for bringing this up, exactly how did they come up with the mean of roughly 15 degrees celsius and why has it been adjusted downward?

  20. Tom Dayton @493 , ~ Quite so.    Even the most intellectually-handicapped member of junior high school classes is capable of understanding the temperatures / anomalies / averages etc which Randman pretends to be confused by.

    But there is a certain entertainment value in seeing the crazy gyrations of the Denialist mind which enjoys displaying itself in public.  A subpontine dweller whose motivation must be at least 50% masochism.


    Randman @whatever ,

    it's been a while since I last checked the NOAA website, and I thought you might be  pleased to read this extract from their latest :-

    "The global land and ocean surface temperature for the first eight months of the year ranked as the second highest in the 138-year record at 0.88 C (1.58 F) above the 20th century average of 14.0 C (57.3 F) — falling behind 2016 by 0.13 C (0.23 F), but ahead of 2015 by 0.03 C (0.05 F).  Based on three simple scenarios, 2017 will likely end up as the third warmest year on record." (unquote)

    Isn't that a beautiful wording, Randman.  

    The same 14.0 degrees that Hansen clairvoyantly predicted in his 1981 and/or 1988 speech, in order (in his kindly way) to show that he was intending to lower the world temperature (from 15.0) so that you would have some "grist for your mill".   [ Literary note : though it is said that "the mills of God grind slowly" ~ yet the Divine mills grind never so slowly as the Randman mills. ]

    But it seems, Randman, that you have a little problem — despite criticizing the world average temperature, you have not specified how you would like the average to be determined e.g. would you like regional temperatures to be summed up over  all the 300 x 300 nautical mile squares constituting the Earth's surface.  Or possibly 300 x 200 n.m. squares as you move away from the equator? Or the 300 x 100 n.m. squares as you get closer to the poles?  Or something more Geodesic? Or less?

    Or would you prefer, Randman, to use the 150 x 150 nautical mile squares ~ as used by NOAA or maybe NASA (or vice versa) ?   I have a vague idea, Randman, that the (Japanese) JMO uses a somewhat different area measurement basis.  Not to mention the Chinese system.

    So which of these measuring systems is the one that you would choose, Randman? They all give a different result for World Absolute Temperature average.  Randman, you are the One — you must choose for us (the red pill, or the blue pill, or some other color . . . in your case, perhaps the rainbow pill? . . . not that there's anything wrong with that! ) .  Which method of averaging, Randman?

    Oh if only the world were simpler, and we had a consensus of scientists to guide us in these matters!


    Oh, er, yes . . . there is one more little problem with your way of "thinking", Randman.   Since you have it somewhere in your head that all of the millions of scientists worldwide are (for decades now) in a Giant Conspiracy to lie to you and deceive your innocence . . . and that you know the Earth is cooling not warming . . . but then how is it that the ice is melting and the sea level has risen several inches since Hansen's pronunciamento in 1981 ?   Just doesn't fit, does it? . . . unless WhatsUpWithThat and Judith Curry are wrong!

    Puzzling, eh!

  21. randman @494.

    You ask of the global mean surface temperature: "why has it been adjusted downward?" The first step in answering that is to identify when it was adjusted downwards. You seem quite adamant that it had not yet been adjusted downwards in 1988.

    With the preview version of Hansen & Lebedeff (1988) we can access the first page of this paper. This paper you argue is using the old 288K estimate for Ts and we can see the resulting global temperature record in Fig 1, from 1880 with an anomaly of -0.40ºC to 1987 with an anomaly of +0.33ºC.

    Happily for us, the successor temperature record, NASA's GISTEMP LOTI, still uses the same 1951-1980 anomaly base. So by examining academic papers citing those LOTI anomalies, it will be easy-peasy lemon-squeezy to spot when this scurilous adjustment was carried out to pervert the climatical reocods of our planet. The adjustment will be very obvious as, with the adjusted anomaly base being calculated to have an average temperature 1ºC lower (14ºC instead of 15ºC), these global anomalies will be boosted upwards by +1ºC.

    A quick look at the latest LOTI release we see that the 1880 anomaly has been adjusted from -0.40ºC to -0.20ºC and that the 1987 anomaly has been adjusted from +0.33ºC to +0.33ºC.

    So when exactly was this GISTEMP LOTI adjustment performed?

  22. MA Rodger, few things. First, how do we know the successor temp record still uses "the same 1951-1980" base, and what is that base specifically in abolute temps?

    Second,  Hansen is a co-author of the 1988 paper you bring up, right? Same year he testified that the 1950-1980 mean was 59 degrees F. Are you suggesting he wrote one thing in his scientific journals and said something different before Congress or what?


    [DB] "Same year he testified that the 1950-1980 mean was 59 degrees F"

    Source citation, please.

    Sloganeering snipped.

  23. Eclectic, so you admit the 14 degrees mean is something they calculate? Finally, and yet you pretend I am the ignorant one here?

    So we saw in 1981 and in 1988, the mean was 15 degrees, at least for the 1950-1980 base. Now it is 14 degrees. Let's keep this simple and straightforward. How they come up with that isn't really a concern at this stage in the conversation. First, we need an agreement on very basic facts. 

    If you won't even admit something was stated, it's kind of silly to get into why and how they came up with the idea, and it seems as if you are trying to suggest something isn't factual and then demand an answer on the details of how such facts should be measured.

    First, let's admit what is factual in terms of the statements and historical views here. 

    Also, I noted your quoted mean is for the 20th century, which throws a small wrinkle into the discussion as we were talking of the 30 years from 1950-1980 and the years following.


    [DB] Inflammatory snipped.

  24. "One of the scientists, Dr. James E. Hansen of the National Aeronautics and Space Administration's Institute for Space Studies in Manhattan, said he used the 30-year period 1950-1980, when the average global temperature was 59 degrees Fahrenheit, as a base to determine temperature variations."

    "Dr. Hansen informed the lawmakers that the first five months of 1988 were the hottest five-month period on record, averaging four-tenths of a degree above a 30-year (1950-1980) norm of 59 degrees Fahrenheit."


    "The British readings showed that the average global temperature in 1988 was 0.612 degrees Fahrenheit higher than the long-term average for the period 1950 through 1979, which is a base for comparing global temperatures. The average worldwide temperature for that 30-year period is roughly 59 degrees Fahrenheit, the British researchers said."


    [RH] Shortened link.

  25. From 1991;

    "The Goddard group found that the record average surface temperature for the globe was eight-tenths of a degree Fahrenheit above the 1951-1980 average of 59 degrees. The British group found it seventh-tenths of a degree higher than the 1951-80 average."

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