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Station drop-off: How many thermometers do you need to take a temperature?

Posted on 24 August 2010 by robert way

An oft-cited skeptic argument is that the decrease in available temperature measuring stations during the 1990s introduces an increased bias towards warming. The argument is based upon the premise put forward by some climate change skeptics that stations which show more warming were kept and ones that show less warming were dropped. The reason this assumption is made is because during the 1990s there was a large reduction in the number of meteorological stations being used for global temperature analyses.

In order to test this theory, several independent researchers (Tamino, Ron Broberg, Zeke Hausfather, Joseph at Residual Analysis and others at the Clear Climate Code Project) and have calculated whether the stations dropped showed less warming than the ones kept. The results? Several find no difference and several find that dropped stations show more warming.

Furthermore, it is also important to note that the methods used in global temperature analyses make them robust to the loss of stations because they use techniques which incorporate multiple nearby stations into analysis of any individual region.

So to conclude: Independent researchers have shown that there is no truth to the claim that cooling stations were removed, in fact evidence suggests that if these stations were included, warming would be shown to be slightly greater.

Note: This post is the Basic version (written by Robert Way) of the skeptic argument "Dropped stations introduce warming bias". We're currently going through the process of writing plain English versions of all the rebuttals to skeptic arguments. It's a big task but many hands make light work. If you're interested in helping with this effort, please contact me.  

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Comments 1 to 19:

  1. "So to conclude: Independent researchers have shown that there is no truth to the claim that cooling stations were removed, in fact evidence suggests that if these stations were included, warming would be shown to be slightly greater." I believe you meant "that if these stations were included, warming would be shown to be slightly *cooler*."
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  2. Crap, just kidding.
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  3. It might be instructive to explain that stations were not really dropped. Rather the Global Historical Climate Network (GHCN), which collects and provides the raw temperature data to the other institutes, was built in ~1992 from retroactive climate records. GHCN doesn’t have resources to manually add millions of data points on an ongoing basis, so they sort of put the GHCN on autopilot thereafter, to receive CLIMAT reports electronically (for surface stations) but the database is supplemented by other sources. It’s largely up to national met agencies which stations they put on the CLIMAT system and how regularly each station sends data. Perhaps 20% (?) of stations automatically feed into GHCN. I suppose at some point they will add some or all of the accumulating manual records.
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  4. The arguments of the statisticians boil down to the hypothesis that the result was not changed by omitting ground stations in high latitudes and high altitudes. As I have pointed out several times before, that is not the point. Can anyone tell me why it makes sense to prune over 80% of the ground stations? Real scientists gather every bit of data available and only discard data for good reasons. NASA, NOAA and the rest have discarded the vast majority of the data without bothering to explain why. Take a look at Peterson & Vose 1997 (An Overview of the Global Historical Climatology Network Temperature Database). While P&V are up front about dropping many ground stations they don't tell us why. I have emailed these good people but they don't respond.
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  5. gallopingcamel #4 "Real scientists gather every bit of data available and only discard data for good reasons." This is incorrect. Real scientists will use the principle of parsimony to ensure that the data they can deal with is both accurate and manageable.
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  6. You have left out steve mosher. Credit where credit is due....
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  7. @gallopingcamel As I understand it. Nobody droped volontary 80% of the station. Essentially, validation process is long and tedious. You need time, manpower and computation capability to do that. Actually, a new version of the database is about to be released. This shoould close the gap. Expect an upward revision of the temperature change. This will certainly creates new claim of manipulation by skeptics.
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  8. If your doctor tells you that you will die in six months, if you don't stop smoking. Do you: A. Throw your cigarettes away and never light another one. (the doctor spent years in school and training so they could tell you this). B. Get a second opinion. (being cautious is a good thing, but the other doctor confirms the first's diagnosis), so you still quit. C. Tell the doctor he's full of shit, and just trying to manipulate you! You've been smoking for decades with no problems, why all of the sudden there's a problem? Hah! D. Get a second opinion, that doctor tells you you only have 3 months to live. Since the two doctors can't agree to the precise time left to you, niether of them know anything, so you ignore them both. C and D seem to be the common choices made! Well, Climate scientists are also doctors, they also spent years in school and training, and they all agree (the real scientists, not creationist morons), that this global climate changes are at least partially if not entirely human driven. We have our second opinion, many in fact. We and our children will pay for our lack of confidence in our own scientists.
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  9. Wynnray, I'll provide some evidence for you. My dad died of oat/small cell cancer last year (97% of such cancer patients have smoked or are/were smokers). He smoked until the last week of his life, during which he was bed-bound, and I refused to give him his cigarettes (he was also on oxygen). He never stopped claiming that it wasn't the smoking. Indeed, and I think this part of the analogy fits in some respects with denialists, he once claimed that the cigarettes were killing the cancer. He once convinced a nurse (she also smoked) in the cancer ward to take him outside to have a cigarette (this was a short time before chemo/radiation took down the mass in his lungs to 2% of its original size -- it later came back with a vengeance).
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  10. gallopingcamel #4, Any hint why they mischieviously ended up with less warming after the drop off?
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  11. #10, Alexandre, you must know it's about the big money these fat cat scientists make. They have to pay for their fancy cars, yachts, and debauchery-filled gambling junkets to Monte Carlo. So they show less warming now so they can get even more money to show more warming later.
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  12. #5: Context is everything. After collection of data for so many years, from so many places on the globe, it seems strange that the science elites decided against automated reporting efficiencies in favor of deleting 2/3 of the land data points. It's curious that they became parsimonious only after launching 4,000 ARGOS and other automated buoys, mostly in the Northern Hemisphere. There's another definition of "parsimony": Unusual or excessive frugality; extreme economy or stinginess. And there's another application of the law of parsimony which was somehow overlooked by the science elite: Stating the simplest of two or more competing theories is preferable and that an explanation for unknown phenomena should first be attempted in terms of what is already known. Theorizing that natural climate change dominates manmade influences would have been a simpler hypothesis to investigate. They way it was framed served to place the burden of debunking the hypothesis on the skeptics. Context is everything. How was the average global temperature record adjusted to replace missing data from Siberia after collapse of the USSR? It WAS adjusted, right, or did the world get that much warmer overnight? Ditto for urban heat island adjustments.
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  13. daisym. You've got the story back to front. The climate *change* science is just an extension of the physics of stable climate. Nobody thought 90 or 150 years ago that working out the physical properties of carbon dioxide (and other greehhouse gases) would lead to where we are now. When all the basics were worked out, it was just wonderful that the earth and its climate were so perfectly suited to life as we know it. It *was* a parsimonious theory. Everything that was learned about the heat absorbing and emitting capacities of CO2 (and the other gases) explained the temperature and what was known of the earth's history. It is just an accident of history that the expansion of learning has coincided with the expanding release of so much CO2 from fossilised carbon compounds. There were other non-polluting technologies available 100 years ago. Had we pursued them instead of fire based power generation, climate science now would be just an interesting side interest of ivory tower intellectuals.
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  14. @daisym The way data are processed removing station has little impact overall. First, climatologist work with the anomaly, which is insensitive to calibration or local climatology. Second, data a weigthed on a area basis. Otherwise, world temperature would be strongly weigthed on USA. As for inclusing data of new sensor, it my not be obvious for you but this is a very tricky process. In addition, data compilation and archiving have a very low priority for grant unless it becomes obvious this is a serious problem. Scientist in every field sufer from that problem. Actually, physicist (which climatologist are a subgroup) fare better than many other type of scientist.
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  15. daisym, understandably you misunderstand the term "dropped" in "dropped stations." It does not mean deleting the data points. For more explanation, see: 1. The second paragraph of the Intermediate version of this basic post (which is linked in the green box at the top of this page you are reading now. Be sure to click the "Intermediate" tab when you get to that page.) 2. My comments here, here, and here. 3. See an actual example of a monthly temperature raw dataset containing not just temperatures for that just-passed-month, but also a large number of data points for months and even years in the past, which are what put the bump in the older end of the distribution of number of stations reporting. If you don't trust that example, then you can download the data yourself.
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  16. #13, 14 and 15: Thanks for your input. Your points are well taken. Tom, I read the information at the links you provided and must concede that it was compelling. It is unfortunate that construction of the temperature record is such a messy business, and has been so poorly explained to the public. Thanks go to all of you for taking the time to share your knowledge with me. Not being a scientist, I have to get information wherever I can. In this regard, all of you perform a great public service through your discussions among each other on this and similar blogs. I have one final question for anyone with the answer: Do the ARGOS buoys measure temperature of the atmosphere at the surface, and (if so) are these measurements included in calculations of the average global atmospheric temperature? I know that satellite and radiosonde measurements are used, but I've not read where buoy measurements are also used. Once again, thanks.
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  17. daisym, I'm glad we were helpful. ARGO measures ocean, not air, temperature. There is an excellent site put up by the Argo project. To answer your question specifically, look at the section How Argo Floats Work. There is an excellent video animation at the Argo home page; click on the little picture at the bottom of the section "Why do we need Argo?" A ton of further info at varying levels of technicality are linked at the left side of that Argo home page.
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  18. #17: Tom: Once again thanks for the links. As you said, there's a wealth of information there, and I've broadened my knowledge. I did not know that they has a life expectancy of 150 cycles. At 10 days per cycle, this translates to something like 4 years. Hopefully, they can be retrieved, refurbished, and reused. I was surprised that these buoys don't measure air temperatures when they surface. Perhaps this is an example of "parsimony"? It seems that an opportunity has been missed to gather unique atmospheric temperature data. Once again, thanks for the information.
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  19. (Replying to GC from another thread but more relevant here). GC - the article you cite shows that dropping the stations doesnt produce a warming bias. However, your post implies that you think that wicked scientists are willfully holding back data that they should be using. However the data isnt in their hands to withhold. To quote NCDC. "The reasons why the number of stations in GHCN drop off in recent years are because some of GHCN’s source datasets are retroactive data compilations (e.g., World Weather Records) and other data sources were created or exchanged years ago. Only three data sources are available in near-real time. The rise in maximum and minimum temperature stations and grid boxes in 1995 and 1996 is due to the World Meteorological Organization’s initiation of international exchange of monthly CLIMAT maximum and minimum temperature data over the Global Telecommunications System in November 1994." (Source here Of course nothing that a willingness to pay more tax on your part to support these data collations wouldn't fix...
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