‘Wrong sign paradox’ finally resolved?

Fig. 3. Cosmic ray flux as measured at two neutron monitor stations.

Even a lay person can imagine how powerful these (already popular) theories would be, if only the data showed exactly the opposite of what they actually show! If the warmest year on record coincided with the strongest solar maximum and not the deepest solar minimum, or if the PDO showed an upward trend over the past 30 years and not a downward trend. But now a solution seems to be in sight.

Solving the mystery

A group of Dutch and US scientists, led by Harry Van den Budenmeyer (Utrecht University), has now proposed a surprising explanation. “At first I did not want to believe it”, Van den Budenmeyer explained to RealClimate, “but once we started to pursue this, things just fell into place”.

The story goes back to the late 1980s or early 1990s (the exact date has not been traced back yet), when a German climate modeller had persistent problems with results of obviously the wrong sign in his model. He was unable to track down the error, so instead he introduced a FORTRAN integer variable called ICHEAT (sorry to get a bit technical, but you really need to understand this) into his computer code, assigned it the value -1 and simply multiplied unruly results by ICHEAT wherever they occurred in his code. Once he’d find the real problem, he would only need to set ICHEAT to +1 and the code would be correct again. But he never got round to fix the problem, his model performed very nicely and over time he forgot about it.

What he did not consider, perhaps understandably at the time: useful computer code spreads like a virus amongst scientists. The code was free for download, hundreds of other scientists started to use it and many only used bits and pieces – nobody ever starts writing scientific code from scratch if colleagues have already solved aspects of the task at hand and the code is free.

“At first we were really puzzled when we found a piece of code with ICHEAT that was used in our lab for climate analysis”, says Van den Budenmeyer. “But once we discovered what it was we started to search more systematically and ask colleagues, and by now we’ve found the ICHEAT bug not just in different European countries but also in California, New York, Sydney and even a Chinese climate centre. We’ve only begun to explore the implications, but I am sure that a lot of the wrong sign paradox that has plagued our science thus far will just go away.”

We will keep you updated here at RealClimate, of course.

p.s. And yes, this is an April fool’s joke, in the Realclimate tradition of pieces like the Doubts about the Advent of Spring, or the famous Sheep Albedo Feedback.

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99 comments on this post.
  1. Pagodroma:

    Such great news on this very day!

  2. Michel Crucifix:

    Strange…. my version of the code has ‘JCHEAT’ but not ‘ICHEAT’. Do I need to change it, too ? A mutation maybe ?

  3. Paolo C.:

    Ahah… ICHEAT…;-)

    I love Van den Budenmeyer/Zbigniew Preisner music, anyway.

    Happy April Fools’ Day.

  4. Slioch:

    Really, this all comes down (or should that be up?) to what I call “northernhemispheriphilia” – the absurd insistence by scientists of ALWAYS showing the Earth with the northern hemisphere on top. If you guys had had the good sense to show the Southern Hemisphere on top then all the signs would have automatically reversed and the problem would have never arisen in the first place.
    Anyway, I think this reversal requires a more thorough analysis, so I’ve alerted the boffins over at WUWT to the situation, who should be able to provide some serious discussion, here: http://wattsupwiththat.com/2012/03/30/open-thread-weekend-9/#comment-941180

  5. Lucibee:


  6. John McManus:

    A giant , invisible bunny , out for his first spring day, explained this to me. Until then it had me fooled.

  7. Alex Harvey:

    Dear Stefan,

    Nigel Calder recently produced a graph apparently from Svensmark and Friis-Christensen (2007) that shows exactly the opposite of your Fig. 3. I asked Nigel here and here if he could explain the contradiction, although I was not entirely satisfied with his response.

    If I may I would like to ask the same question here. How is it that Svensmark and Friis-Christensen have a graph that appears to contradict yours. Please don’t tell me it’s the ICHEAT bug. :) But it surely must be explained what they have done that is wrong.

    [Response: There is of course a real correlation between the 11-year solar cycle (which also modulates the cosmic ray count) and global temperature – quite a few papers have shown this, including recently Foster&Rahmstorf (ERL 2011). -stefan]

  8. Deen:

    IF(today.EQ.”20120401″) THEN

  9. Jeff Pierce:

    I’m confused. The comparisons showing the wrong sign above are between solar activity, PDO and cosmic rays with the temperature record, all observations. How would a bug in the code of climate models affect these comparisons since everything shown above is observations?

  10. Geoff Russell:

    In commercial computer code, where people are trying to avoid litigation for copying proprietary code, the concept of “Clean room” development is well understood. You lock people away from net access and have them develope the functionality you want to copy from scratch. Sounds like some climate modelers need to try the method … or at least do some serious code analysis looking for shared sections and have them reimplemented independently.

  11. Marco:

    It would have been so much better if you’d just had the name of the Dutch scientist right. It is Van den Budenmayer!

    How can we believe anything you say if you can’t even get the name right? Pah!

    [Response:Must be a different guy. I’m talking about the colleague mentioned in the acknowledgements of this paper. -stefan]

  12. Dallas Dunlap:

    It’s probably a bad idea to publish satire in a climate blog. In a few days thisarticle will by cited on WUWT and pompously editorialized about on Forbes. It will end up being the 2123rd “final nail in the coffin” of AGW theory.

  13. chris:

    Good to have this sorted at last. Have to say ‘though, that the ICHEAT methodology has been a great help in efforts to extract useful interpretations from recalcitrant data as attested, for example, by the outstanding efforts of Drs Roy (Julie) Christie and John (Woy) Spencer, not to mention the clever applications of Professor Mitt Linzwest (and others).

    And it’s great to see how this very special-ised methodology has been embraced by the hoi polloi, to such an extent that a complete absence of scientific insight is no longer a hindrance to the very productive data “re-interpretation” that we see at all corners of the Internet!

  14. Russell:

    You should publicize those first graphs more, perhaps make it a quiz where people have to guess the trend in them after they are shown the temperature trend. Is there any reason to think that PDO is affected by the CO2 or the sun/cosmic rays?
    If they are all uncorrelated then it won’t be pretty if they all point the same way. What temp rise per decade would we get then.
    (thought you were just going to say the the temp graph was upside down because the satellites were programmed in the wrong hemisphere)

  15. Cugel:

    This seems to have spread into my bank’s software as well. I’m going to demand they release their code, but with no great hope that they’ll comply :(

  16. Ben Bastian:

    As a game developer I’ve done the same thing many times. It’s pretty common in programming – most non programmers don’t appreciate that when you only have 1s and 0s -1 is as good as 1, but takes up half the memory. All of the really cheap sites on the web use -1s and the letter o. It keeps the costs down. Happy -1th of April.

  17. jiminy:

    Not so new, first proposed by Avril le Fou

  18. Darryl Williams:

    Nice april fools joke.

  19. pieterzijlstra:

    April Fools’ Day!?

    But anyway a good check on knowledge and logic.
    I am a lay person!


  20. Pepe Larios:

    Are de GHG, stupid

  21. anoNY:

    Brilliant, ANOTHER climate conspiracy from the alarmists! I aim to be the Prometheus in this situation, by which I mean I will deliver your remarks straight to Fox News for immediate dissemination.

    However, being a humble man, I will not use my own name, as I wish no fame for myself for reporting this “discovery.” Also, I wouldn’t want to get famous on this particular day, since April is of course Hitler’s birth month.

  22. Dan Bloom:

    While we argue and discuss this and that, seemingly going around in circles, but also maybe getting somewhere, step by step, here is my new book about POLAR CITIES that everyone dismissed so vehemently three years ago.

    TRAILER VIDEO for “POLAR CITY RED ” – sci fi novel by Jim Laughter

    POLAR CITY RED info link:

  23. Spencer:

    I’m missing something here, how does an error in the code for a computer model make a difference in the observational data series you’ve shown? Has ICHEAT been used to produce final numbers for all these data? That is, has the PDO etc. been different than we thought? You really need to explain things better before weird memes propagate.

  24. Brian Brademeyer:

    I am not sure I grasp the relevance of a computer bug to the data measurements shown in the Figures above.

    Could you elaborate on just what the “paradox” of data observations being anti-correlated with expectations has to do with a computer fudge factor?


  25. GSW:

    Gillard has obviously taken your important new finding seriously.


  26. Kevin McKinney:

    As a resident artsie here at RC, I share your embarrassment not a whit!

    However, in order to begin to right the cosmic balance again (so to speak), I will ask a (perhaps foolish) question: does this mean that the long-standing and very well-accepted ‘pirate effect’ and ‘sheep albedo effect’ are now of the wrong sign?

    If so, your travails are surely not over…

  27. Larry Coleman:

    Let’s see now…today is what?

  28. Dave123:

    A very dangerous April Fool’s joke. Betcha Watts swallows it….and from then on it will be immortal in the blogosphere

  29. Arun:

    The people who think Stephen Colbert is a conservative will take ICHEAT to be fresh evidence of a scandal.

  30. wili:

    I was about to sputter with rage, but then I noticed the date–nice one!

  31. Hans Kiesewetter:

    Nice ;-)

    I was reading the last few lines when I suddenly realised, that also this theory will be falsified. Very soon, I think. Maybe already tomorrow.

  32. Christopher Squire:

    Re; ‘ . . We will keep you updated here at RealClimate, of course.’

    Once a year will be quite enough, thank you.

  33. Chris Colose:

    Thanks for the hard work RC.

    Unfortunately, I believe you have the start date incorrect. The issue pre-dates Van den Budenmeyer by a couple decades. There are also reports from the astronomical community coming out that ICHEAT has been applied even earlier to the faint young sun “problem,” but it turns out stellar luminosity actually goes down with time!!

    This correction now explains why Mars has evidently cooled over geologic timescales, and beautifully explains the transition from greenhouse to icehouse climates over the last several tens of millions of years. It turns out that Earth is inevitably headed for a snowball state sometime soon, depending somewhat on the size of the sheep-albedo feedback (though some new minor issues open up in explaining previous, similar events).

  34. Ric Werme:

    I project that next week someone will get real and find the Fortran variable UCHEAT in another program available as an undocumented tuning parameter.

  35. Caleb:

    I have to say that, while potentially embarrassing, I would much rather this news be broken honestly, on a reputable climate science blog like this one, as opposed to entering the media through some denialist source. Mistakes are part of the scientific method, and I’d much rather our side keeps the moral/scientific high ground by being honest about mistakes when we find them. So, thanks for posting this.

  36. Mitch Lyle:

    Is this an April fool joke? Could you show a graph of a climate variabile where ICHEAT is -1 vs +1? You have only shown graphs where the system does not respond as naively expected.

  37. KSchlonz:

    Didn’t expect German climate crooks to have humour.

  38. John E Pearson:

    Love it. Had to check the date!

  39. The Elf:

    I think you and your colleagues have more work to do. Please consider the first letter of “iCHEAT”. Everyone knows i is an imaginary number!

  40. John McManus:

    Dave123 @28:

    I always figured that every Watts post was an April Fool joke and he just hasn’t figured how to use a calender.

  41. chris:

    Alex Harvey @7

    Good to see you joining in with the April 1 jokes! Svensmark and Friis-Christensen did indeed use the iCHEAT method.

  42. Alan:

    I’m not sure why everyone is releived? This is terrible news! Now we know for sure that it’s the Sun, there is sweet FA we can do about it.

  43. KnockJohn:

    Yes Elf i is an imaginary number. That is why the version that Michael Crucifix has is jCHEAT – He must have the engineering edition.

  44. Salamano:


    Well done. :)

    Time to see who it spreads to.

  45. passing:

    I saw the ICHEAT as a reference to Fortran using variables beginning with I…J as integers.

  46. Craig Nazor:

    This ICHEAT seems to be a useful subroutine – to bad it has been exposed. When word about this gets out to the deniersphere, this is going to create problems. Think of the headlines it will make: SCIENTISTS SCREW UP THEIR DATA USING ICHEAT! OMG, all those hefty paychecks from the government will dry up, and all you guys will have to get REAL JOBS!


    On a more serious note:

    How many climate change deniers does it take to screw in a light bulb?

    None. They only know how to screw the planet!

  47. Daniel J. Andrews:

    Dang! You had me for a bit. Not till I started reading the cosmic ray section did I realize what you were doing. :-) Nicely done.

  48. vukcevic:

    Looks like as the latest Forbush decrease has confirmed the Svensmark’s hypothesis.

  49. John P. Reisman (OSS Foundation):

    Amazing, I made it all the way to the line about solar activity and ran right smack into the words ‘coincides with the deepest solar minimum’ when I realized the paradox was the relationship between the science outlined in the article and the time segment on a per anum scale. If the time segment occurs on a particular the ‘Wrong sign paradox’ make perfect sense to those that understand the coincidence factor. This also proves that if you choose your data correctly correlation handily proves causation.

    The relationship immediately became obvious and suddenly I realized that we’ve all been thinking about this wrong-headedly. This goes to the opposites attract theory. When two opposites come together in a binding relationship it is well known that bliss ensues until of course the opposites come to the notion that they do have something in common – the fact that they are opposite. This is akin to anti-matter/matter interaction at that point.

  50. Susan Anderson:

    po’ po’ po’

  51. David Wilson:

    delightful! thank you.

    then there is the law of inverse deniers too – how long it took one to see through your excellent good humour.

  52. John P. Reisman (OSS Foundation):

    I need to do a talk on belief structures next week. Where can I download this code… or is it hidden?

    ICHEAT: Illusory Code Enables Alternative Translation

  53. Alan Henderson:

    I have it on good authority that the iCheat methodology was hijacked by the Republican party for use in deciding the suitability of its presidential nominees.

  54. piffy:

    tiswl TOTALLY get cited by teh deniers.

  55. Louis Hooffstetter:

    The bug in my code says:


    “Nope, D’jew?”

  56. Richard Woods:

    @52 John P. Reisman

    “ICHEAT: Illusory Code Enables Alternative Translation”

    Perhaps you meant:

    ICHEAT: Illusory Code Heuristically Enables Alternative Translation

  57. csoeder:

    I LOL’d.

  58. t marvell:

    Very funny. But not so funny. In the real world the ICHEAT is more complicated, and the researcher might not be aware that he/she is using it. There is always a tendency toward confirmation bias. There is always a tendency to accept one’s research results if it reaches what one expects or wants, and a tendency to fiddle with the research if not.

  59. Andy Lee Robinson:

    or, to go with the tinfoil:

    ICEHAT – Illusory Code Enables Heuristically Alternative Translation

  60. CM:

    Plus/minus one of your best, though nothing beats the sheep albedo.

  61. Snapple:

    Not to interrupt or anything–but you need an April thread.

    They have an alligator farm in Michigan because of global warming. Some of the alligators have been pulling people’s legs…


  62. R. Gates:

    Well, this is certainly going to leave some April foolie day egg-yolk on someone’s face…

  63. Jos Hagelaars:

    Funny piece, I prefer the German word ISCHUMMEL above ICHEAT or even the Dutch word IKLETSKOEK.

    The Dutch are famous though for their problem solving capabilities, after tackling this ISCHUMMEL problem, our scientific institutes are directing their attention on the monster of Loch Ness and the location of Atlantis, but our top priority will be to finally solve the famous chicken and egg problem.

  64. Bob Tisdale:

    Stefan: While I do realize this is an April Fools post, a note of clarification about your second example.

    You wrote, “Basic physical considerations would suggest that the global temperature is warm when the PDO-Index is high, i.e. when sea surface temperatures in the North Pacific are high. A theory that would beautifully fit the data – if only the sign were reversed (Fig. 2)!”

    The PDO does not represent the sea surface temperature anomalies of the North Pacific. In fact, the PDO is inversely related to the detrended sea surface temperature anomalies of the North Pacific, north of 20N.


  65. Steve Fish:

    I have been mining the Bore Hole to try to work up the data for a new RC original post entitled- “Wrong spin paradox finally resolved?”

  66. John P. Reisman (OSS Foundation):

    #56 Richard Woods

    ICHEAT: Illusory Code Heuristically Enables Alternative Translation

    Yes, my apologies, my IFLOP software was enabled when I typed that.

  67. Andy:

    This is no “sheep albedo effect” but still clever.

  68. richard pauli:

    I knew it!

    Finally you must have come to understand that gravity is just a theory.

    So much more work to do.

  69. Tony O'Brien:

    JCHEAT Do not forget many Euopeans pronounce the J as we would a Y

  70. Chris Dudley:

    I actually looked at the code and, unfortunately, every instance of ICHEAT was multiplied by the variable NCHEAT which also was assigned the value -1.0. I’m afraid the problem has not yet been solved.

  71. Tenney Naumer:

    Very Van-y!

  72. Lucien Locke:

    Oh Stefan,

    The iCHEAT is just to much to bear. I laughed until my sides hurt…you are too much……

    still laughing,


  73. Susan Anderson:

    Saving some excellent advice for the upcoming Open Thread:

    teensily OT here but useful nonetheless.

  74. tokodave:

    Wow. The mountaineer, backcountry skier and mountain biker in me always thought the rule: Gravity never takes a day off was sacrosanct….but now I’m not sure about that either! ;-)

  75. owl905:

    I’m saving my sympathy for the guy who has to tell Arthur Dent the answer was really -42.

  76. Noel Fuller:

    Google has its own subtle sense of humour too. When I pasted Van den Budenmeyer to google it searched Van den Budenmayer then asked if I really meant Van den Budenmeyer!


  77. Dan H.:

    I must admit that the sheep albedo effect is my favorite, although there were several other goodies. Gotta love today.

  78. dhogaza:

    Dan H.

    Gotta love today.

    In your case, it’s sort of like Groundhog Day blended with April Fool’s.

    Having read so many of your posts and all.

  79. dhogaza:

    Apple will be announcing the iCheat in Q3 2012 … since scientific computing requires so much computational horsepower, it’s iRack mountable.

  80. DF:

    You RC guys are just cruel.

  81. Christoffer Bugge Harder:

    #7 Alex Harvey

    Perhaps Calder did not see any pressing reasons to reveal to you that the “impressive” cosmic rays/temperature fit of Svensmark and Friis-Christensen in their never-published reply to Lockwood & Fröhlich was only achieved by removing a trend of 0,14C/decade – or 0,7C over the last 50 years? ;)


    Best, Christoffer

  82. Ron Manley:

    It ill behoves me to criticise such an august body of scientists as those who run Realclimate.org but I feel it incumbent on me to do so. You are indeed correct to state the variable ‘ICHEAT’ has appeared in all climate models up to the present but are completely wrong about its provenance. It was introduced by Dr CO Jones and Professor SN Dall and should read ‘1 C heat’ and represents the CO2 climate sensitivity built into the models. In 1988 the neo-Confusion philosopher, Jim Han Sen, introduced the following line: ‘WATVAP=3.0”. Climate sceptics claim that as there has been no warming since 1998 its value should be 0.0.

  83. Slioch:

    Oh dear. My attempt, mentioned at #4 above, to get the WUWT site commenting on this didn’t get very far, see:

    “Slioch says:
    April 1, 2012 at 2:45 am

    May I draw everyone’s attention to the fact that there has been a major reversal in climate science reported at Realclimate here: http://www.realclimate.org/index.php?p=11329

    REPLY: This is a badly executed April Fools Joke, ignore it. Here’s why I didn’t do one this year:


    With so much deception going on, you’d think RealClimate would know better. I guess not. – Anthony”

    Perhaps Anthony was concerned lest his followers fell for it, though, to be fair, they had not done so in the hours before he added his reply.

  84. sydb:

    ICHEAT2 is also a very useful variable. If you set it to 0 and then use it as a multiplier, all sorts of things can simply disappear. There are times when that is more useful than simple ICHEAT. For example, it would be difficult to interpret CO2_conc *= ICHEAT;
    but CO2_conc *= ICHEAT2;
    has a very simple interpretation. There isn’t any CO2, so it can’t be doing anything.

  85. Marco:

    @Stefan-inline response to #11:

    This is quite funny, there IS such a person as Van den Budenmeyer in climate science?!

    I was convinced you were alluding to Van den Budenmayer, a fake composer made up by Zbigniew Preisner and Krzysztof Kieslowski.

    There I was, thinking I made a smart remark pointing out I looked through the April Fool’s joke, and the joke is STILL on me…

    [Response: Admittedly, the VdB acknowledgement in that old paper was inspired by Kieslowski… Don’t tell anyone! -stefan]

  86. Jbar:

    Ha ha. (But EVERY day is April 1 for climate skeptics!)

  87. Jim Larsen:

    Susan on Trolls,

    The wrong sign paradox applies to trolls, too.

    By observation, at least a few people on any blog will respond to trolls, thus providing sustenance. An individual who is bothered by this is best served by adding to the din, as that will hasten the troll’s exile to the Bore Hole.

    Be that as it may, I don’t think Dan H and Norman are trolls, and from their actions, it seems that the mods at SS & RC agree. Norman was ejected for being too high-maintenance. Hopefully he’ll learn to shrink his bandwidth.

  88. steve:

    Better check those voting machines for ICHEAT, too

  89. Phil Hoey:

    Having done computer modeling in flow dynamics I know you do have to sometimes force the model to behave like the real word – especially when have to satisfy a CPA that the finacal output is accurate. I almost bought into it until I realized ‘oh sugar’ what is today’s date!!! LOL

  90. Kevin McKinney:

    “…the 2123rd “final nail in the coffin” of AGW theory…”

  91. Jim Ramsey:

    It’s important to understand that this ICHEAT code must only be applied an odd number of times, otherwise it is totally ineffective.

  92. Hengist:

    I’d like to refer you to Lou Grinzo here :
    “If you’re going to do an AFD joke, make it funny and make it subtle enough to actually fool people.”

    I don’t think RC should attempt April Fools gags. The topic is (a) serious (b) tough enough to understand for the layman . But there’s a (c) Funny doesn’t work in a polarized dialogue, not because it’s not funny, but because it creates a them and us mentality, or the them and us mentality that’s already there becomes more polarized. Or something like that.
    I’ll give you an example from my own experience. To face down unruly litigants the ‘State’ uses humour in the courtrooms. Ive been there, and I cant quite explain why it works. If you don’t get what I’m saying, sorry, were I to explain what Im on about I would go way off topic of RC. Now Im not saying Ive had my SOH lobotomized but put it this way have you ever lied when someone’s asked “D’you get the joke?”


  93. Jim Newman:

    Oh my gosh. How embarrassing. And to think I sent this to 4,374,210 people…
    What a great example of obfuscation.
    My friend, Willy Wonka, would truly have appreciated this.
    I look forward to next year’s rant.

  94. Timothy:

    Ha! You had me fooled – mainly because this bit is all too true:

    “useful computer code spreads like a virus amongst scientists…nobody ever starts writing scientific code from scratch if colleagues have already solved aspects of the task at hand and the code is free.”

    I’m sure there are a few bugs out there that have spread in this fashion.

  95. Eli Rabett:

    John McManus says:
    1 Apr 2012 at 4:59 AM

    A giant , invisible bunny , out for his first spring day, explained this to me. Until then it had me fooled.

    Eli did not! It was a secret.

  96. Radge Havers:

    I’m definitely not a computer person, but it seems that there may also an issue in the design tolerances for what look like remnant loops: SEPTIC_FOO and SEPTIC_BAR. Specifically the escape counter using the variable DUM_NUM seems to have been left in a default with lots of 9’s in it. Perhaps if you’re going to leave those functions in there, setting a lower limit for SUM DUM_NUM would shorten runtime and thereby avoid overtaxing the heat sinks… at least on some of your more antiquated systems.

  97. Ed Beroset:

    As one of the people involved with the code review on this important topic, I thought it would be useful to give an update. It seems that far too many extant papers and theories rely on this particular variable essentially inverting non-conforming data, so rather than eliminating the variable, it seemed better to rename it to more accurately describe its function. Henceforth, this data-inverting variable shall be called KONTRARIAN. (Patches available on request.)

  98. George M:

    i may be an imaginary number but the author of the post isn’t. In any event, joke or not, better vetting of the climate model computer code, numerical estimations, and actual validation would be a good idea all around.

  99. Mike:

    If you’re going to print April Fool jokes, please pull them after 1 April. Maybe I’m just a curmudgen, but reading the article on 22 April is no longer funny, just a waste of time.