No Consensus among Three Global Precipitation Datasets

Global precipitation is a crucial part of our understanding of the global Water Cycle. The climate science community can’t hope predict how precipitation will change in the future without knowing how precipitation has varied in the past. The oceans are a crucial part of the water cycle. As the USGS notes in their webpage The Water Cycle: The Oceans:

It is also estimated that the oceans supply about 90 percent of the evaporated water that goes into the water cycle.

For land and oceans, NOAA presents three satellite- and rain gauge-based precipitation datasets that start in 1979, giving more than 3 decades of data. I’ve included 2 of them in past posts: (1) CAMS-OPI, which stands for Climate Anomaly Monitoring System (“CAMS”) and OLR Precipitation Index (“OPI”); and (2) Global Precipitation Climatology Project version 2.2 (GCPC v2.2). The third is CPC Merged Analysis of Precipitation (CMAP).

Amazingly, there are few to no agreements among the three datasets when looking at the global data. Each shows different annual variations, Figure 1. [Note: Only one of the three datasets is updated regularly at the KNMI Climate Explorer (CAMS-OPI), thus the different end dates of the data.]

Figure 1

Figure 1

And their trends are very different, Figure 2.

Figure 2

Figure 2

The CMAP data shows a large decrease in global precipitation anomalies from 1979 to 2009. The CAMS-OPI also shows a decrease, but it’s not as great as the CMAP data. And the GCPC v2.2 data shows basically no trend, when compared to the other two.

IS ONE OF THE DATASETS CLOSE TO BEING RIGHT?

Looking at the global combined land plus ocean data, one would be hard pressed to determine if any of the three global precipitation datasets are close to being correct. But there is a place where we may be able to get some insight. Because of El Niño and La Niña events, precipitation in the tropical Pacific is very volatile, but it should also follow a pattern: precipitation should increase during El Niños and decrease during La Niñas. And some El Niños should have stronger impacts on precipitation than others.

Figure 3 presents the CAMS-OPI, CMAP and GCPC v2.2 precipitation anomalies for the tropical Pacific. Again, the three datasets have been smoothed. Before 1987 and during the 1988/89 La Niña, the CMAP data is the outlier. On the other hand, the CAMS-OPI data diverges from the other two during the early 1990s and from 1998 to 2003. That leaves the GCPC v2.2 precipitation data.

Figure 3

Figure 3

The GCPC v2.2 precipitation anomalies for the tropical Pacific are compared to NINO3.4 sea surface temperature anomalies in Figure 4. Both datasets have been standardized (divided by their standard deviations). The NINO3.4 data reflect the impacts of El Niño and La Niña events on the sea surface temperature anomalies of a region along an east-central portion of the equatorial Pacific, and they are a commonly used index for the timing, strength and duration of El Niños and La Niñas. As shown, the GCPC v2.2 precipitation anomalies for the tropical Pacific mimic the variations in the NINO3.4 data. There are differences, but the tropical Pacific precipitation data are consistently responding to El Niño and La Niña events, as one would expect.

Figure 4

Figure 4

Those ENSO-related variations also carry to the global GCPC v2.2 precipitation data, but we have to isolate the land and ocean precipitation data. See Figure 5, which is from the post Models Fail: Global Land Precipitation & Global Ocean Precipitation. As noted in that post:

Looking at the global ocean precipitation anomalies (red curve), it’s blatantly obvious that the primary causes of annual precipitation variations are El Niño and La Niña events. The 1982/83, 1986/87/88, 1997/98 and 2009/10 El Niño events are plainly visible, and you can also make out the lesser El Ninos in the early 1990s and mid-2000s. The trailing La Niñas are also evident.

The opposing relationship between ocean precipitation and land surface precipitation is also obvious. Land surface precipitation generally drops in response to El Niños and increases during La Niñas. There is also a strong dip and rebound in the land surface precipitation data starting about 1991 that may be a response to the eruption of Mount Pinatubo. Curiously, the ocean data does not show a similar response.

Figure 5

Figure 5

Unfortunately, there are no land and ocean masks at the KNMI Climate Explorer for the CAMS-OPI and CMAP precipitation data, so we can’t see how they respond when broken down in similar fashions.

CLOSING

For global land plus sea surface temperatures, there is a reasonably close agreement among the datasets. No such agreement exists for global land plus ocean precipitation data.

Without knowing how precipitation has varied in the past, how then can climate modelers hope to be able to project changes in the future?

And if global precipitation is dependent on El Niño and La Niña events, climate models would have to be able to simulate the processes of ENSO. But after decades of modeling efforts, they still cannot simulate those El Niño- and La Niña-related processes. Refer to Guilyardi et al (2009) Understanding El Niño in Ocean-Atmosphere General Circulation Models: progress and challenges.

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30 thoughts on “No Consensus among Three Global Precipitation Datasets

  1. But how can you dare bring science into a discussion of downpour events. Sorry I cannot flutter my hands appropriately. Thanks as always for some facts and great charts, oceans at work again who would have guessed they had anything to do with downpour events.

  2. Is it possible to know if a large area where there is no population is going through a drought? An area such as the Pacific Ocean? Or how such a drought might migrate/behave over time?
    It seems to me, regardless how much we measure, we don’t seem to measure enough.

  3. Looking at anomalies gives no sense of the significance. Is it a big worry if the trend really is negative 0.054 mm/day per decade, as CMAP data set suggest? How does this figure compare with total precipitation?

    Also, these charts offer no support at all for the logical theory that global warming leads to an increase in precipitation because it causes more evaporation . How much belief should be given to that theory?

  4. “Without knowing how precipitation has varied in the past, how then can climate modelers hope to be able to project changes in the future?”

    very simple. Without knowing how C02 had effected temperature in the past, Arrhenius, by understanding the physics, predicted that if C02 increased, temperature would increased.
    Similarly, the author of this climate model (http://climateaudit.org/2013/07/21/results-from-a-low-sensitivity-model/) did not have an uncerstanding of how C02 had changed temperature in the past, but that didnt prevent him from

    A) writing down his best albeit imperfect understanding of the physics
    B) Using that to make a prediction.

    Understanding the past if not a logical prerequisite to making a prediction.
    And further, if they had had a good observation series I’m sure someone would accuse them of tuning.

    So, of course one can hope to predict without an understanding of the past. That hope is improved if you have a good past record, but a record of the past is not logically required and nothing follows from its absence.

  5. But even Arrhenius changed his mind regarding the impact of CO2 on Earth’s temperature. After much prodding from Angstrom and many hours in the lab.

  6. David in Cal says: “Looking at anomalies gives no sense of the significance. Is it a big worry if the trend really is negative 0.054 mm/day per decade, as CMAP data set suggest? How does this figure compare with total precipitation?”

    Sorry. I had actually created the comparison graph of annual global precipitation (not anomalies):

  7. Good analysis, Bob.
    Steven Mosher: You are absolutely correct that hypotheses can be constructed from “first principles” without any use of historical data. But somewhere along the line you need to test the hypothesis against observations, or you really haven’t learned much from the exercise. Bob Tisdale’s article raises a few questions regarding the measurement system.

  8. Mosh, a long time ago my company build a process plant using a totally new concept. Six people started up the plant but could not get it to run correctly. After six weeks they quit trying and went home. I was dispatched to the plant with a purchase order book without monetary limit and told to fix the plant no matter what it took. I did not have to approvals from anyone about anything. I started testing systems. It did not take me very long to understand that I needed a baseline to understand what was going on. After establishing baselines for each system, I was able to sort out the underlying problem was too many feedbacks in the process system preheat and heating system. The designer was trying to save too much energy. I shut the plant down and reconstructed the feed lines and heat exchangers. That helped tremendously. I then tested each system against a new baseline and found other problems with fired heaters, cooling towers, refrigeration systems. I fixed each system in 11 weeks total. The plant ran like a jeweled watch.

    First principles are fine but baselines are indispensable for understanding complex process problems and feedbacks. I see the earth’s climate as a complex process system with feed forwards and feedbacks. My belief is that some measured data is required to understand it. If not, then one can get fixated on one variable like carbon dioxide and develop confirmation bias about other variables such as natural cycles.

  9. Mosher, would you let us know when all the factors that impact climate are known? Until then your comment is pretty useless.

    A drop in precipitation is one more factor in support of Miskolczi’s theory of a constant greenhouse effect.

  10. Yes, you can predict w/o understanding the past. However, the great fault of climate modelers and climatology in general is prediction without adequate understanding of the natural processes that bear on the question. Thus the failure of the climate models.

  11. @David in Cal

    If I might be permitted to make a IPCC-style ‘Projection’, I can show with Bob’s (worst-case, CMAP) trend that there will be no rainfall at all in 465 years!

  12. It doesn’t matter any more.

    According to the latest theory:Either the heat occasionally hides in the ocean or natural variability overcomes water vapor amplification. Explainificating the pause is top priority right now. /sarc

  13. Just a side note. Don’t let it derail the discussion.
    Ecclesiastes 1:7
    Not a bad observation for a “primitive” non-scientist.

  14. Thanks, Bob.
    If I’ve done my sums correctly, 0.1 mm/day of precipitation/evaporation amounts to a required latent heat of vaporization of 2.6 Watts/sq meter (averaged over 24 hours). Those seem like fairly significant numbers in this context given the differences between the data sets.

  15. “Arrhenius, by understanding the physics, predicted that if CO2 increased, temperature would increase.” [Stephen Mosher at 7:50AM 7/23/13]

    Arrhenius made a GUESS. He was wrong.

    Current physics says that increases in atmospheric CO2 lag behind temperature increases by a quarter cycle.
    [Dr. Murry Salby, “Relationship Between Greenhouse Gases and Global Temperature,” lecture, April 18, 2013, Hamburg, Germany]

  16. Thank you, BOB TISDALE, for more excellent scientific analysis. You are a true Warrior for Truth in Science.

  17. Side Note 2:
    Mr. Din (whose first name is NOT Gunga — smile), side note noted. That wise man had the inside track; he knew the Designer. And there will never be another like him. I. Kings 3:12. He proved the maxim that “to those who have, more will be given,” Luke 19:26, i.e., he was wise, therefore, he asked for wisdom.

  18. Steven Mosher [July 23, 2013 at 7:50 am] says:

    “Without knowing how precipitation has varied in the past, how then can climate modelers hope to be able to project changes in the future?”

    very simple. Without knowing how C02 had effected temperature in the past, Arrhenius, by understanding the physics, predicted that if C02 increased, temperature would increased. Similarly, the author of this climate model (http://climateaudit.org/2013/07/21/results-from-a-low-sensitivity-model/) did not have an uncerstanding of how C02 had changed temperature in the past, but that didnt prevent him from

    A) writing down his best albeit imperfect understanding of the physics
    B) Using that to make a prediction.

    Understanding the past if not a logical prerequisite to making a prediction. And further, if they had had a good observation series I’m sure someone would accuse them of tuning.

    So, of course one can hope to predict without an understanding of the past. That hope is improved if you have a good past record, but a record of the past is not logically required and nothing follows from its absence.

    There is clearly a theme in your comment there Steve. The theme is that the past, and what actually occurred, is unimportant. I suppose this is the next angle to explain away all the actual observed climate variability that already occurred which inconveniently spoils the AGW cult agenda of blaming man for spoiling the static climate on Earth.

    It’s a damn good thing we actually found evidence of past drought, flood, ice ages and little ice ages, etc ( striations in Central Park, glacial deposits, canyons, valleys, Great Lakes, to mention but a few ), not to mention the momentous discovery of Continental Drift. Because if not, one could only imagine how far along the AGW cultists would be with their doomsaying agenda. BTW, this is why I believe that the three biggest heroes of Science in the last century were Milankovic ( astronomical influences ), Wegener ( continental drift ) and Alvarez ( impact events ), because they injected a critical dose of reality into the narcissistic human-centric Science community where man is King and believes the world revolves around him. But I digress.

    It sure sounds to me that your hypothesis of not really requiring past data is describing a game of chance, like say Roulette, when someone sets about predicting what numbers shall occur next. Aside from those rare celebrated cases exploiting wheel bias there are countless fools that look at the posted table history, torturing the numbers looking for patterns, using everything including pure voodoo to get to their magic formula. If you were aiming your hypothesis at them I would be right with you! And the reason I would agree with you is because those folks are classically missing the forest for the trees, the actual discovery they should have extracted from the data is that the observed short term trends ( recent results from table ) mean nothing at all for predictability, forwards, backwards or anything else ( again, barring bias or cheating ).

    But your hypothesis applied to climate science misses the forest for the trees as well because the natural variation present in the historical record is the point, and is precisely what you will miss by discounting past results ( e.g., Mann chucking the MWP and LIA to construct a hockey stick ).

    The Roulette zealot or Lotto player is easily fooled by seeming micro-patterns of numbers in past results even though the fact is that a number might even come up multiple times in a row ( and this gets interesting and familiar because some will then favor that number repeating again and others say it is removed from the pool of possibilities ), and the climate zealot is much the same as they make wild leaps from patterns that they are living through. But believe it or not, the Roulette or Lotto zealot is much closer to sanity because at least their data has unambiguous raw data for historical results whereas the climate zealots are altering and then cherry picking the “raw data” even before they begin their own statistical voodoo.

    BTW Steve, I’m no grammar n*zi but isn’t the exchange of “affected” and “effected” a cardinal sin for an academic of English?

    To Anthony, I just thought of a great cartoon for Josh! … Michelangelo … MichaelManngelo … chipping away the MWP and LIA to reveal the David statue hockey stick that was there all along! Please tell him he can have have it. Apologies in advance if someone else already thought of it ( but I honestly cannot recall seeing that yet, honest! ).

  19. Nice refutation of Mr. Mosher, Blade. I admire your mental energy. I momentarily toyed with the idea of reasoning with Mr. Mosher, but, realizing all the time it would take (me, anyway!), I bailed. Way to go, Brains of Steel Blade.

    And, GREAT cartoon idea!

    Tell Josh (went to his site for the address): If you want to get in touch my email is: josh [at] cartoonsbyjosh.com

  20. Gunga Din says:
    July 23, 2013 at 2:05 pm

    Just a side note. Don’t let it derail the discussion.
    Ecclesiastes 1:7
    Not a bad observation for a “primitive” non-scientist.
    —————————

    Two verses earlier (KJV):

    Ecclesiastes 1:5

    5 The sun also ariseth, and the sun goeth down, and hasteth to his place where he arose.

    Psalm 19:1-6:

    1 The heavens declare the glory of God; and the firmament sheweth his handywork.

    2 Day unto day uttereth speech, and night unto night sheweth knowledge.

    3 There is no speech nor language, where their voice is not heard.

    4 Their line is gone out through all the earth, and their words to the end of the world. In them hath he set a tabernacle for the sun,

    5 Which is as a bridegroom coming out of his chamber, and rejoiceth as a strong man to run a race.

    6 His going forth is from the end of the heaven, and his circuit unto the ends of it: and there is nothing hid from the heat thereof.

    Joshua 10:11-14:

    11 And it came to pass, as they fled from before Israel, and were in the going down to Bethhoron, that the Lord cast down great stones from heaven upon them unto Azekah, and they died: they were more which died with hailstones than they whom the children of Israel slew with the sword.

    12 Then spake Joshua to the Lord in the day when the Lord delivered up the Amorites before the children of Israel, and he said in the sight of Israel, Sun, stand thou still upon Gibeon; and thou, Moon, in the valley of Ajalon.

    13 And the sun stood still, and the moon stayed, until the people had avenged themselves upon their enemies. Is not this written in the book of Jasher? So the sun stood still in the midst of heaven, and hasted not to go down about a whole day.

    14 And there was no day like that before it or after it, that the Lord hearkened unto the voice of a man: for the Lord fought for Israel.

    Job 38:22-23:

    22 Hast thou entered into the treasures of the snow? or hast thou seen the treasures of the hail,

    23 Which I have reserved against the time of trouble, against the day of battle and war?

    Is it primitive to think that the sun crosses over the earth, then hurries during the night outside the solid dome of heaven back to where he must rise again to run his course across the sky, entering through the same window in the firmament as before? Or to imagine that hail & snow are stored up in treasure store houses to be released when God wants? IMO “the oceans are not full” doesn’t indicate an understanding of the hydrological cycle, but appreciation for the mysteries of God’s ways not yet understood.

    Still awaiting your defense of Intelligent Design, Ms. Moore.

  21. If natural variation (unknown) can hide/eliminate CO2 forcing’s effects, then it is always in control, the Null Hypothesis. As it is unknown, it may have unknown multiples more power/influence than it has just “demonstrated”, and is always the First Order influence.

  22. Dear Milodon Harlani,

    Your simplistic reading of the Scripture you quoted above (8:48PM) shows a lack of understanding for what the language (Hebrew) it was written in meant and also a lack of comprehension of the use of metaphor in writing. The Bible often uses symbolism and poetic description to describe complex reality in simple, representative, terms.

    You also, I think, a priori, exclude the possibility of God’s being able to do ALL THINGS. “All things” would include being able to suspend everything in the universe, if He wanted to, in order to stop the earth from turning and the moon from orbiting, etc… etc… (ALL you could mention, He could do) in order to grant Joshua’s request. If you believe in God, you must believe God can do all things, for that is part of the definition of “God.” Otherwise, you believe in “god.” I am not trying to persuade you that God is. I am only getting our terms defined for accurate communication.

    I would LOVE to discuss Intelligent Design with you. Until A-th-y invites us to do that, however, except for quick comments here and there, I am going to refrain. It would be abusing our gracious host’s generous hospitality to launch off on a topic he has NOT introduced nor encouraged. Further, I am not an expert in intelligent design.

    Here are some scientists you can listen to or watch if you want to learn about ID:

    Stephen Meyer

    David Berlinski

    David Berlinski with Michael Behe and Stephen Meyer
    Part 1

    Part 2

    Jonathan Wells

    I hope you find the above helpful in your search for truth.

    Your ally in the battle for Truth in Science,

    Janice

  23. Thanks Bob. Fig 5 is particularly intriguing.
    There is an approximate antiphase precip relationship between land and ocean
    The ocean data shows a quasi regular bi-annual oscillation with the occasional tri-annual interregnum. But it doesn’t relate to the QBO, I checked.

  24. Janice Moore says:
    July 23, 2013 at 11:28 pm

    My reading of Hebrew scripture is not simplistic, merely accurate & literal. The word translated by Jerome as “firmamentum” came from the Greek Septuagint’s “stereoma”, since he didn’t know Hebrew. Both words imply strength or solidity. The Hebrew is “raqia'”, which is an onomatopoetic word meaning “hammered out”, similar to but obviously not cognate with English “racket”. Hence, the vault of heaven is like a stadium dome.

    In the Bible, the sun enters the dome through a window, travels over the flat earth, the floor of the stadium, then exits through another window & travels outside the dome back to the place of his rising. Outside the dome are the storehouses of rain, snow & hail, which God opens to let the precipitation fall. The waters of the sea come from wellsprings beneath it. The Book of Enoch, which was very popular with Jesus’ sect the Essenes, lays this all out in detail, but it didn’t make it into the Masoretic text of the Old Testament (relied on in Protestant translations), as compiled AD 600 to 1000, although bits of it appear in the New Testament books of Jude & James. Enoch went straight to heaven like Jesus, so Christian-era Jewish scribes didn’t like the book.

    The flat earth-dome cosmology was standard in the ancient Near East, with local variants. In Egypt, the sun traveled under the earth to return to the place of his rising. The biblical version comes from Chaldean Babylon, where Judean captives imbibed Mesopotamian mythology.

    Do you imagine I haven’t heard before all the ID lying spew you posted? You challenged me over my citation of Behe’s anti-scientific example of “irreducible complexity”, the bacterial flagellum. He appears in your video, so please, let’s hear your defense of this inanity.

    I must admit that the first time I saw electron microscopy of a bacterial flagellum, I laughed out loud, it looked so machine-like. But the scientific reaction to this observation is to try to understand the molecular biochemical, genetic pathway through which the structure evolved, not to throw up your hands & concede defeat, punting by saying that God must have made this irreducibly complex feature. Discovery of the pathway could lead to great health benefits, if it could be interrupted.

    In fact there is not just a single bacterial flagellum, but many different flagella, which have evolved separately. The best studied flagellum, that of E. coli, contains forty proteins, of which it shares twenty-three with other bacterial flagella. Just two are unique to flagella. The others closely resemble proteins which carry out other functions in bacterial cells. Hence, most components of a flagellum probably already existed in bacteria before this structure evolved. The other two clearly evolved from proteins previously present through simple mutations’ being naturally selected for.

    Some of the components of a typical flagellum, eg the “motor”, the apparatus for extruding the “propeller” and a primitive directional control system, can perform other useful functions in the cell, such as exporting proteins. Thus, flagella probably evolved from bacterial protein export systems, with helpful functionality at each stage of development. I haven’t studied the problem for some time, so it may be that at least in E. coli the evolutionary pathway has been reconstructed based upon its genome. Or not. It doesn’t matter. The point is that there is no scientific reason for believing that God zapped flagella into existence. Only religious faith.

    This was Behe’s best example of his hypothetical “irreducible complexity”, which fact demonstrates the anti-scientific nature of this concept hatched to make creationism look more scienc-y.

    No non-religious scientists have embraced ID because it’s not science. As the Dover trial hilariously showed, ID was simply concocted to try to sneak creationism into public schools.

    You said you’d love to tell me all about ID, but now claim not to be an expert. There can be no experts in anti-scientific cant. Only shameless liars & anti-scientists like the individuals in your clips.

    I hope the moderator will let this pass. Its point is the science, not the religion. It’s relevant because understanding how anti-scientific is ID helps explain the vicious ad hominem attacks on Dr. Spencer, whose work on climate should be the focus of discussion, not his religious faith.

    Yours in the pursuit of truth, knowledge & wisdom,

    MDH

  25. As I said, I didn’t make my “side note” to derail the thread, so I won’t respond along these lines beyond this. (Apologies to Bob Tisdale for any “derailing” I may have caused.)
    PS Ben Stein is Jewish.

  26. Gunga Din says:
    July 24, 2013 at 9:14 am

    Quite true that fundamentalist Jews, Muslims, Hindus & some other faiths also don’t believe in evolution. That’s why above I wrote non-religious rather than non-Christian.

    But what bearing does that have on the scientific fact of evolution?

    I didn’t play your linked video, but I saw Stein’s film, No Intelligence Allowed. It seems to me that what he has trouble with isn’t evolution, but abiogenesis, the origin of life, which evolutionary theory is not about.

    As you may know, the Anti-Defamation League condemned the movie’s abuse of the Holocaust and its imagery. Its statement read, “Using the Holocaust in order to tarnish those who promote the theory of evolution is outrageous and trivializes the complex factors that led to the mass extermination of European Jewry”.

    The doctrine of eugenics was the false scientific fad of its day in the early 20th century, comparable to CACCA today. “Darwinism” is a fantasy. Darwinian evolution is a meaningful term, used to refer to old-fashioned, continuously observed natural selection (“directional evolution”), as opposed to new-fangled (from the Modern Synthesis with population genetics, c. 1920s) but equally well observed stochastic evolution (from statistical effects such as genetic drift, reproductive isolation, the founder’s principle), etc.

  27. Gunga & Janice, if I may call you those names:

    Have you never wondered why God zapped into existence the pathogenic bacterial flagella that ID (TM) finds so irreducibly complex?

    Could it have occurred after the Fall, when because of Adam & Eve’s sin, death, disease, suffering & all manner of evil entered the world?

    Hard otherwise to think of a reason for God to intervene in natural evolution to make these structures. But as adepts if not experts in ID, maybe you can offer a better reason.

    Do you see why Dr. Spencer’s embrace of the Book of Genesis & other portions of the Bible as science creates (!) such problems for skeptics?

    I do enjoy your comments, but feel that you should try to put yourselves in the mindsets of scientists rather than believers. The problem with the Church of CACCA is the same kind of simple, faith-based orthodoxy as is sadly evident among fundamentalists of all denominations.

    BTW, real biblical fundamentalism considers the Bible not literally true, but “inerrant”, if properly interpreted.

  28. { Steven Mosher says:
    July 23, 2013 at 7:50 am
    “Without knowing how precipitation has varied in the past, how then can climate modelers hope to be able to project changes in the future?”

    very simple. Without knowing how C02 had effected temperature in the past, Arrhenius, by understanding the physics, predicted that if C02 increased, temperature would increased.” }

    OMG-LOL
    His physical analysis considered only a closed system and extrapolated to the atsmosphere, and any experiments were done in a closed experiment, not in a chaotic environment.

    Get real.

  29. Given the dominant role that water vapour plays in the total greenhouse gas forcing, an inability to come up with a consistent dataset describing merely how water vapour leaves the atmosphere, much less its other behaviours, makes it very difficult to claim reliability for any modelling attempt.

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