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Debunking this skeptic myth is left as an exercise to the reader

Posted on 17 December 2010 by John Cook

I recently received an email proposing an alternative cause for global warming:

"The real reason for global warming is the earth's orbit around the sun is slowly decaying, and the earth is being pulled closer to the sun."

It's fairly straightforward to determine whether this is actually occuring using direct measurements. Without wanting to give away too many details (for reasons that will soon become apparent), I cited some empirical observations that falsified the "decaying orbit" hypothesis. His response:

"This is where we must agree to disagree. I measure the progression of earth's decaying orbit by the surface temperature, and by the increase of the surface area the sun is warming. Houston is near the equator. Our winters are becoming sunny, and warmer."

I queried why he relies on these indirect methods and ignored the direct measurements I cited. The response:

"I ignore direct readings, because I feel it flawed."

I was never able to extract from him why he felt the direct measurements were flawed, other than a general "I'd rather depend on my own senses" sentiment. But I've intentionally left out the details of my response as I thought I'd leave it as an exercise to the reader as to how you would respond to the argument that global warming is being caused by a decaying orbit. I'd be interested to see what different approaches others take.

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Comments 1 to 50 out of 54:

  1. Hi John,

    To my opinion, two opposite factors will influence the distance earth/sun.
    First : the sun is becomming bigger due to the mass loss with about 4 % every 1 billion year (*wiki). So if the earth would keep the same orbit, the surface of the sun would be closer of course.
    However, there is a second effect, the equilibrium between the centripetal force (mv*v/r) and the gravitational force (Gm1m2/r*r). So if the mass of the sun is becoming smaller, the gravitational force decreases which will induce a larger orbit (to decrease the centripetal force).
    Of course the latter can also be achieved by reducing the speed of the earth but i think that that is very easy to verify.
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  2. Well, the obvious reply is that the earth's orbit *is* decaying, but very, very slowly - it's not likely to be a problem for at least half a billion years or so, I'd guess (to pluck a number out of the air - anyone who feels like doing the research will quickly be able to find something more meaningful).

    However, it's a constant process. Even if there *was* any significant forcing as a result of orbital decay, it certainly couldn't explain the rapid upswing in the warming trend over the past decades...

    And that, of course, completely ignores the circularity of his reasoning: "The earth is warming because it's orbit is decaying, and we know the orbit is decaying because the earth is warming..."
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  3. Kepler’s 2nd law of planetary motion: orbital period squared is proportional to semimajor axis cubed. Roughly that means that the length of a “year” is proportional to the distance from the Sun. Where a “year” is here defined relative to the background of fixed stars (sideral). I kind of think we’d have noticed the year getting shorter.

    Mercury 58 million km from Sun (OK so it varies a lot at 0.21 eccentricity)* and surface temperature ranges from about -180 deg C (night at pole) to about +430 deg C (noon at the equator).

    Venus 108 million km from Sun (i.e. gets a quarter of the sunlight that Mercury does). Surface temperature quite uniform day/night pole/equator at about 460 deg C.

    Remind me what the physical difference between Mercury and Venus is? Oh yes. Venus has an atmosphere. And what is the major constituent of the cytherean** atmosphere? Go on, have a wild guess.

    *Whereas John will pull my comment if I speculate upon that of the questioner.
    ** I learned so much from Kuttner/Moore.
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  4. If earths orbit were decaying to the extent that it alone was responsible for global warming, then one would expect an increase in solar radiation at the earths surface which has been observed (Pinker 2005) but one would also expect that radiation to show consistent increase over the last 50 years.

    Measurements show that solar radiation reaching the earths surface showed a decline until 1993 and some increase in the following decade. During the period of decline in solar radiation, global temperatures rose. Decay of the earths orbit could not have produced global warming which occurred from 1963-1993

    Further, the increased solar radiation reaching the earths surface since 1993 has been less than that required to account for the rise in global temperatures. This shows that change in the earths position relative to the sun have been too small to account for temperature increases.

    Ergo, rising greenhouse gas concentration accompanied by an almost linear rise in temperature remain the most logical explanation.
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  5. I would ask: if the earth's orbit is decaying, then why is the upper atmosphere not warming at the same rate as the lower? Why are nights warming more than days? Why are winters warming more than summers?
    With thanks to the new Skeptical science guide for clarifying these points for me!
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  6. I kind of think we’d have noticed the year getting shorter.

    Bah, Doug beat me to it.
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  7. I'd go with Bern's point about circular reasoning as the main problem. He's not understood the most basic point about spurious correlations.
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  8. We have satellites around Earth. If they measure more heat from the Sun, then more heat is arriving.

    This could be the Sun heating up, or us getting closer, or a combination. 'It's the Sun' explains why... it's not the Sun.
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    Response: This is the answer I went with in my email reply. But interesting to read the other responses - circular reasoning, length of year, the lack of solar fingerprints, surface measurements of solar radiation - this hypothesis is falsified on many levels. I should throw out a few more skeptic myths, see what readers come up with as an interesting exercise (might save me some work too :-)
  9. One more reason - if the earth's orbit were decaying (shades of Star Trek !!) at a rate sufficient to cause the observed warming, then AGW is the least of our troubles !
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  10. Apart from what others have already mentioned, I would have asked him what kind of globe he is looking at where Houston is "near the equator". But, then, it might just depend on his definition for "near"! Oh, and also, how relevant one specific location is when we talk about something global.
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  11. So we all promise to avoid circular arguments?

    There is a favorite refrain on this website which goes it's the multiple lines of evidence that support AGW. I except the basic premise of the point but every time it's used as an argument to defend a criticism of any one particular line of evidence it seems to lose it's power.

    The use of circular arguements on the "The human fingerprint in the seasons" comments started to really bug me.
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  12. I agree with #9. Earth orbit apsis must be decaying some 0.2% per century -some 10 km a day- to get a warming effect the same order as observed. This reasoning cancels positive feedbacks with system inertia because "I feel" they are similar. Isn't i-feel-ogy epistemologically correct from a hedonistic point of view?
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  13. My reasoning would be similar to MarkR above: the closer sun would mean more W/m2 of energy getting here, and we do not observe that.

    OTOH, if we were getting closer, but that did not change the irradiance we get, then it's irrelevant to the point.
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  14. This is debunked very simply: there's no consensus.

    As shown by Iorio 2009, "the Earth's perihelion position is displaced outward by 1.3 cm along the fixed line of apsides after each revolution."

    We must therefore wait a million years or so to see which interpretation is correct.

    In the meantime, this page is of particular relevance here:

    The earth is shifting on its axis (40 miles per year). Twelve o’clock noon use to be the hottest part of the day. Now three o’clock in the after noon is the hottest part of the day. This is due to the earth shifting on its axis. The earth is also wobbling on it axis. This was discovered before the Chilean earthquake in 2010. I discovered it on the internet in 2008.

    At this rate, the hottest part of the day will soon be midnight. Pigs will fly. The oceans will turn to lemonade. Because everyone knows that anything discovered on the internet must be true.
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  15. This one is easy to debunk. Earth position relative to the Sun is known within a few meter. There some discussion that there is a drift but I would be the order of a few meters per year at most.

    Astronomers are paranoiac about the Earth motion in space. Actually, there an international services only working on this issue.

    You will see on this web page that the Chilean Earthquake did not change the duration of the day by the way.
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  16. John and all others, a lot of patience sounds in your words ... I would have lost my temper ... congratulations to you! excellent job
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  17. #17: Mike, there is some friction in outer space.

    You can disperse energy by collisions with objects, by tidal heating or, most consistently we are slowed slightly by the light pressure from the Sun.

    Because we're going around the Sun, sunlight actually strikes us at a slight angle to our trajectory at any point in time. In effect, there is a tiny component of the light motion that is opposite to our direction. This transfers momentum to the Earth, slowing us down.

    There is also the small light force from the Sun pushing us directly outwards, but that is technically not friction since it doesn't depend on our velocity, but on our position...
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  18. This argument seems to be similar to another I ran across, that it was space debris causing the warming. Though i don't remember the exact reason they said it was causing the warming. Friction as it entered the atmosphere? Adding mass to the Earth causing the days or orbit to change? Whichever it was there was nothing that could shake them from that belief.
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  19. But if feels to me like the years are getting shorter. ;-)
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  20. This is clearly wrong, because another, often ignored theory is right. Given the upcoming holiday season, I think it's time that everyone face the fact that global warming is caused by Eurasian Leprechaun Farts (ELFs).

    The evidence is indisputable. The greatest warming is at the north pole (home to the jolly old ELF himself, and his vast army of worker ELFs). It began coincident with two known changes in ELF behavior, a dramatic increase in population, and a switch in diet to coprolite consumption (which itself may have caused the population explosion -- a very deadly positive feedback). Different camps argue fiercely over which of these is the true, underlying cause, but the fact of the matter is that ELFs are deadly.

    The scientific impacts of ELFs on the earth's atmosphere as SBD gases (silent but deadly) was proven hundreds of years ago by Arse-nius, and is not really subject to rational dispute. Those who emphatically profess otherwise are merely, so to speak, cutting the cheese.

    Of course, the nefarious fossil food industry is expending vast sums of money to keep this hushed up. And when they can't keep it up, they try to confuse the common man by recasting the debate in emotional terms as a War on Christmas!

    Whether it is the increase in Eurasian leprechaun population or the newly found leprechaun delight for their products, the fact remains that any proper solution -- a reduction in coprolite sales and consumption -- will hurt their recent huge upswing in profits from coprolite mining and distribution. Their entire financial empire will crumble if the problem is addressed, as it must be if we are to save civilization as we know it.

    People need to wake up to this! Admit that ELFs are the problem and curtail the fossil food industry now, before it's too late!
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  21. Excellent way of distracting the deniers. Lets have more of these.
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  22. Length of year came to my mind, too.

    But this dude's from Texas, so you have to put it in terms he can understand.

    If he were right, they'd be playing high school football in the morning, and his houston texans would start games in the middle of the night, by now.

    If you can't explain it with football, people from Texas will *not* understand you.
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  23. I'm originally from Texas. I'd be mad at you if you weren't... well, sort of right.
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  24. If the Earths orbit has been decaying and this is causing warming .. wouldn't we expect the Mesozoic to be colder than now ?
    That would have been tough for the dinosaurs...
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  25. This all kind of goes back to what I was saying in the article I did on Why Does Anthony Watts Drive an Electric Car? The more solid the evidence for climate change becomes the more extreme and outside the realm of science the challenges will be. You see that here with the silly claim that the Earth's orbit is degrading. And I think we increasingly see it with people like Steven Goddard and Anthony Watts. Same with Spencer, Michaels and others.

    Watts' recent irrational post over the difference in the anomaly between UAH and GISS is a perfect example. He's so intent upon finding a problem, because his whole world view is based on AGW being wrong, that he skips very basic, utterly elemental steps, like adjusting for differing base lines. (Sorry, I know that's OT.) And worse, when it's pointed out, rather than saying "whoops, sorry that was a silly mistake on my part" he goes overboard trying to defend his mistake.

    I think the climate change issue is rising to a new level lately. The science is even more solid than ever. That means there is probably going to be an equal and opposite reaction the likes of responses like these.

    I predict a whole new series of denier issues are going to start coming to the forefront soon.
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  26. "I measure the progression of earth's decaying orbit by the surface temperature"
    He is taking the temperature decrease as a proxy for the orbital decay. More than circular reasoning this is simply a faulty assumption.
    But let's assume it is correct. In the last century we experienced a rate of warming of about 0.5 °C/century. If it is due to the orbital decay, it cannot be a new phenomenon, it has been going on for millennia. A thousand years ago, then, it was 5 °C colder than now, i.e. we were in the middle of an ice age, the famous Medieval Ice Age. Going a thousand more years back, it was 0 °C on average; here you can clearly see the origin of the iconic snow covered Christmas trees in Palestina. :)
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  27. #27: "If it is due to the orbital decay, it cannot be a new phenomenon, "

    Ha! Now someone has to work out the orbital decay rate that provides the appropriate increase in radiative forcing -- and project that forward to see how much time we have left.
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  28. @HR: that is not circular reasoning, but the affirmation that, indeed, many lines of reasoning support AGW. It is not in itself evidence, but rather a declaration that the evidence exists, and that it is plentiful.

    If you think that is circular logic, that might explain why you seem to have such a hard time grasping the relatively simple aspects of AGW theory...
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  29. muoncounter
    we have T^4 ∝ S ∝ r^2 where S is the solar constant and r the distance from the sun, currently 1 AU; so T ∝ r^1/2. Let call A the constant of proportionality, so T=A*r^1/2. We currently have T=288 K and r=1 AU from which we know that A=288 K/AU. Taking the first derivative with respect to t (time) and noting that dT/dt=0.5 K/century we can easily obtain dr/dt=3.5*10^-3 AU/century. If Venus orbit doesn't change, we'll be there in 80 centuries (8 Kyrs). Forget about the next ice age (and much more!).
    But ... the IPCC is wrong and in the next century we'll get just another 0.5 °C of warming. Mission accomplished.
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  30. #30: "we'll be there in 80 centuries"

    It will be sooner than that, I fear. The rate of orbital decay will accelerate as we draw closer, as this theory (if I may call it that) suggests that the sun's gravitational field overwhelms the earth's magnetic field (in previously some unknown way).

    This is groundbreaking stuff; if this guy is right, he's got a lock on the Nobel (in literature, if not physics). We'll be looking back on 2 or 3 deg C of warming as a pleasant day at the beach. I suggest hoarding large blocks of ice (I hear there's a big one floating off Greenland) as a refuge of last resort.
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  31. So Immanuel Velikovsky would be sort of the patron saint of this sound theory.

    I wonder why all the supposed physical phenomena behind these theories resemble something devised by Ming the Merciless, evil ruler of Mongo. Epistemological hedonism?
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  32. The writer is relying upon instinct as opposed to empirical evidence. But instinct can be fooled. I have supplied a link to a documentary that looks at climate change issues from an Inuit perspective. More than one elder notes the belief that the planet has shifted on it's axis, and some cite reasons. Insofar as the observation that the sun now sets in a different place, this is explained by the fact that the atmosphere is warmer and thusly refracts the sun's rays differently. There are other examples in this documentary that illustrate the breakdown of instinct's.

    This certainly doesn't provide an answer to your question John. I do hope it sheds some light though.

    Inuit Knowledge and Climate Change
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  33. @ muoncounter: Next you'll be tellin' me that the moon is in the 7th house and Velikovsky's Jupiter will collide with Mars...
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  34. My pet theory is that the extra air exaled by all of those extra people (try graphing population, CO2 and temps some time) adds to the mass of the Earth. This, coupled with the GHG effect of the literal Anthro CO2, is driving up temps in lockstep with population. Feels good to finally let that out...
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  35. Daniel... I'm almost ashamed to admit that in response to denier claims I've actually done rough calculations for how much CO2 is exhaled by humans. Suffice to say even that didn't satisfy those whom I was trying to convince. But maybe it had an impact on someone else reading the comments online. //sigh//

    What's the saying? If you wrestle with pigs you only get dirty, and the pigs generally enjoy it.
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  36. My skin is starting to sag and I'm getting shorter. Therefore gravity is increasing. I know my skin and height are good proxies because they are responding as predicted for an increase in gravity.
    Note that I get shorter at night and my skin doesn't get less saggy during the day, both of which contradict predictions of the decaying orbit idea.
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  37. Yooper, you've completely failed to take into account the heat and water vapor content of that exhalation. I like to use the Saturday Night analogy. Imagine a car (station wagon, circa 1975) parked out on the cliff overlooking town. It's Saturday night (winter), and the glass windows are rolled up on the car. Normally, the GHG content of the car's atmosphere would be at 280ppm (because Anthony can't usually get a date). However, tonight is special. The atmospheric CO2 and water vapor content inside the car is rising rapidly. Longwave radiation emitted from the surface of the heat engines inside the car is being absorbed more and more by the GHGs, and the radiative pathway is getting longer and longer. The interior of the car begins to heat up. The dashboard figure at the north end of the car begins to melt. The back window, at the south end of the car, begins to ice over--except at the edges, where the car's interior material is soaking up LWR and transferring it conductively into the glass. The car begins to rock in an almost Milankovitchian rhythm. Precipitation begins to drip off of the dome light and other features (after all, the troposphere can't expand in this simulation -- no analogy is perfect). Suddenly, at the tipping point for runaway heating, mitigation occurs! No--it's not what you're thinking. A police officer throws a door wide open, and the car's atmosphere quickly returns to pre-date temperatures.

    Will the police ever throw our collective car door open, or are we completely . . .
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  38. #34: "the moon is in the 7th house and Velikovsky's Jupiter will collide with Mars... "

    Hey, Velikovsky sightings are your beat, especially after you challenged someone over those 'In Search Of' clips.
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  39. Re: muoncounter (39)

    Ah, the misbegotten jewels of an ill-spent youth...still have the likes of Graham Hancock and Von Daniken in the ready-at-hand arsenal with the offspring of Howard and Burroughs not far behind...(Pellucidar anyone?).

    Speaking of tipping one back, don't mind if I do. Febrile mind, here I come...

    The Yooper
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  40. Re: DSL (38)

    1. If the semi-mythical car for the mythical date had a ragtop...
    2. Would that be waste heat then from the car's engines? ;)

    Still think it's Scooter (Phil Rizzuto) doing the play-by-play.

    The Yooper
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  41. Rob @36, I did this in 2006 in Eos (the newspaper of AGU). The editor and I had a ball with this one. It was sent out for peer review with one reviewer genuinely unsure what my intent was. It was hacked down from a much longer original.

    I begin with the observation that enteric methane is included in Kyoto and move on to suggest that therefore the US should call for the inclusion of human respiration CO2 in Kyoto as it would do relatively more damage to creditors like China.

    The saddest thing I found was that there are 40 nations with total population 750 million (12% world total) and total GDP 370 billion 1995 USD (i.e. 1.1% 2006 world total) where the population respire more CO2 than they release from fossil fuels.

    I had a couple of follow up emails from folk who appeared to umm bat for the other side and were put out to find it wasn't something they could use.
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    Moderator Response: [muoncounter] fixed link See also our Does breathing contribute to CO2 thread
  42. The simple counter-argument is that if global warming were due to a decaying orbit, it wouldn't have accelerated rapidly over the past 30 years. It would be an extremely slow, constant rate of warming, not a sudden rapid acceleration.
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  43. Isn't the Earth-Sun distance increasing due to tidal forces (and to a smaller extent solar mass loss)?
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  44. The irony is there is an orbital change of some sort thats been going on for the last 1000 years that should currently be causing a cooling, cant remember or find the paper someone may know.
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  45. a bigger solar disc should have effects on solar eclipses (not being total anymore), and several ancient monuments like Stonehenge should have to be rebuild
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  46. the simplest counterargument (one that everyone can understand the logic to) is that if the Earth's orbital decay is sufficient to cause 0.8C/century warming we would have been a ball of ice 2000 years ago
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  47. #40: Yooper, you and I apparently misspent our youth in much the same way. Although The Hollow Earth (fact or fiction?) would explain why the Arctic ice is melting -- heat from the internal sun!

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  48. Doug Mackie
    I was not aware of the potential use of human respiration emissions in such a way. Luckly, no one dared to use it.
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  49. Speaking of The Hollow Earth, perhaps the warming comes from the internal sun becoming a red giant in spite of its size :)

    The fact is we live in times when epistemological hedonism[1] is king so any book describing global warming as a hoax will reach larger publics the same way Velikowsky's or Von Däniken's books would sell copies ten times the best selling book devoted to debunk their theories. And in a similar way, Watts' paraphernalia gets 2 million hits a month, while RealClimate gets 360K and this site 220K[2]. People has been swollen by this tide of epistemological hedonism and -placing their necessities, including that of recognition, above everything else- they simply write to the head of a website to share the preposterous theory they took a fancy to. The same about some people commenting and the dumbpiphanies they sometimes provoke.

    I wonder if analyzing the attitudes behind denialism and the underlying mechanisms is not as important as spreading good science about what causes global warming causes and discussing solutions.

    [1] THE LIMITS OF CRITICAL THINKING by Jamy Ian Swiss Swift 1-1, page 14
    [2] Wattsupwiththat; RealClimate; SkepticalScience
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  50. #50: "analyzing the attitudes behind denialism and the underlying mechanisms"

    Here's a relevant definition:
    denial /de·ni·al/ (dĭ-ni´il) in psychiatry, a defense mechanism in which the existence of unpleasant internal or external realities is kept out of conscious awareness.

    That's a fascinating area of study, but probably not what John had in mind for this discussion.
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