The other day, I was scrolling through The Website Formerly Known as Twitter—which I tend to do after sharing my blog posts there, since it seems the polite thing to do—and I saw a “tweet” or an “X-udate” or “X-cretion” or whatever one calls them now, that asked, “Do you believe in global warming?”

Such questions always seem bizarre to me.  It’s similar to the old, “Do you believe in UFOs?”  Though, with the latter, one can always snarkily reply, “Why, yes, I believe in unidentified flying objects.  I think people often see things in the sky that they cannot properly identify, especially if they are not experts and conditions are not ideal.”  But really, even that sarcastic response misses the point and can be misleading, so it’s best to be avoided.

The problem is, the question entails a kind of category error.  The reality of global warming—by which I assume the questioner means some form of anthropogenic climate change—is an empirical question.  It is a statement about reality itself, and is either true or false whether or not anyone even knows about it as a possibility, let alone “believes in it”.

It’s more reasonable to ask, “Do you believe that anthropogenic climate change—AKA global warming—is happening?”  That, at least, is a sensible question, when using the form of the word “belief” that means that, based on the evidence and reasoning one has available, one has arrived at the provisional conclusion that global warming is happening (or is not).

In using this term “belief”, one would usually imply that one is reasonably convinced, but open in principle to alternative explanations and counter arguments and new evidence—as one always should be in matters of empirical fact, at least if one is committed to always trying to make one’s map describe the territory as well as possible (to borrow a phrase from Eliezer Yudkowsky).

But when people say, “Do you believe in…” something, it doesn’t come across—to me at least—like a question about facts, but rather as a question about ideologies, about team membership, about religion, in a way.  It can be at least excusable and appropriate, if still rather nonsensical in my view, to ask someone if they believe in Santa Claus, or in Communism, or in God.  It doesn’t necessarily have anything to do with external reality other than the state of certain people’s minds, but at least it’s reasonably appropriate.

The absurdity of this conflation of “believing in” something with an assessment of a thing’s actual reality is pointed out well in Terry Pratchett’s delightful Discworld novels—in either Wyrd Sisters or Witches Abroad, if memory serves.  I don’t recall how the point comes up, but it relates to belief in the gods of Discworld.  The narration says that, of course, witches knew that the gods were real, they had dealings with them, they sometimes met them.  But that didn’t mean there was any call to go believing in them.  It would be like believing in the postman.

If someone were to ask me whether I think that climate change is real, and why I think whatever I think, I might reply that the general consensus of the world’s climate scientists—people who actually specialize in the area—seems to be that it is happening, and though their most specific predictions can be highly uncertain, as can all specific predictions in science beyond the realms of simple linear dynamics, most of them conclude that it is really happening.

I read a statement once that claimed that the percentage of climate scientists who are convinced that human-caused global warming is really happening is higher than the percentage of medical scientists who are convinced that smoking tobacco increases the risk of lung cancer.  I don’t know whether that statement is true, and I don’t recall the source—it sounds more like a rhetorical point than an actual argument, which makes me suspicious.  If it is true, it’s remarkable in more than one direction.

One can look up in journals the papers and the data that is being gathered and analyzed by climate scientists.  Google Scholar works nicely for searching out real, published scientific studies on almost any amendable topic.  One can also go to pre-print servers such as arXiv, to see papers that have not yet been peer reviewed.

If one is judicious, one can even find decent science news in less technical publications—phys.org seems to be pretty good—but mainstream reporting on such things is often unreliable and inconsistent, since after all mainstream media exist primarily to sell themselves, not necessarily to promulgate the most rigorous truth they can uncover.  Even Scientific American has turned into a twisted mockery of its former self.

I understand at least some of the physics behind the “greenhouse effect”, without which the Earth would be uninhabitably cold.  Visible light passes through the atmosphere without interacting much with the gases therein—which is why air is mostly transparent, other than the modest scattering of blue light that leads to the sky’s daytime color (and inversely to the color of sunsets).  But such relatively low-entropy, high frequency light is absorbed by the ground, then reemitted as higher entropy, lower frequency light, such as infrared, which is much more readily absorbed by molecules like CO₂ and H₂O and methane (CH₄).  The reasons for this are quantum mechanical in nature, but the fact that it happens is basic physics that’s been well known since before anyone currently alive was born, as far as I know.

And so, these atmospheric gases heat up (and in turn heat up the other atmospheric gases) until the outer surface of the atmosphere is warm enough to radiate out as much energy as comes into the Earth.  Such is the nature of so-called black body radiation.

But for the outer atmosphere to be warm enough to do this, the middle atmosphere must be warmer, and the layer below warmer still, and so on, since outer layers radiate inward as well as outward.  The outer layer of the atmosphere will always be just warm enough to radiate out just as much energy as the Earth receives in light from the sun; if it were not, the Earth would rapidly get hotter until a new equilibrium was reached.  The final radiating surface might end up being higher in the atmosphere, which would mean that, closer to the surface, things would be warmer.

Anyone who has dressed in layers in cold weather should understand this intuitively.

[By the way, there may be some slight imprecisions in my very quick summary above of the thermodynamics of atmospheric gases, so if any experts in the matter would like to make any corrections—especially if such corrections are truly substantive—please feel free to do so in the comments.]

There are other atmospheric effects that are even easier to understand at basic chemical levels, such as the fact that increasing CO₂  concentration leads to increasing acidification of the oceans.  This is fairly straightforward chemistry—carbon dioxide, when dissolved in water, partially reacts to form a weak acid—“weak” meaning just that the hydrogen ions do not completely dissociate from the molecule H₂CO₃*.  This can be demonstrated easily by getting some pH paper (readily available at all high street pH paper shops), testing some neutral water (to confirm its baseline neutral pH) and then blowing through a straw into the water for a few minutes.  You can then check if the pH has dropped, which—if you are a typical mammalian creature from Earth—it will have done.

I think this experiment can also be done with phenolphthalein, which is wine-red when in a basic (alkaline) solution and clear when in an acidic environment.  You can do a sort of magic trick, turning “wine” into “water” with just your breath through a straw bubbling in a glass.  Don’t drink it, though.  I don’t think phenolphthalein is particularly dangerous, but I wouldn’t want to endorse someone imbibing it.

I’m not going to tell you my conclusions about the empirical fact of whether or not “global warming” is happening and how and why and all that.  You can explore the subject as a homework assignment (but don’t hand it in to me).  But I will tell you my conclusion, which is probably obvious, about “believing in” things.  I don’t believe in “global warming” nor in the lack thereof.  I don’t believe in Santa Claus.  I don’t believe in Capitalism or Communism or Socialism or Fascism or Scientism** or Antidisestablishmentarianism.  I don’t believe in the Tooth Fairy, and I don’t believe in life after love.

And I really don’t believe it’s useful or good or anything but an irrationality to “believe in” matters that involve claims about the nature of reality itself.  Reality is that which exists whether or not anyone believes in it—indeed, whether or not anyone exists to be capable of believing in it.  That’s why it’s reality, as opposed to fictions and ideologies and other abstract concepts of various kinds.

I know*** that Amazon delivery people exist.  That doesn’t mean there’s any call to go believing in them.

* H₂O + CO₂ ⇌ H₂CO₃ ⇌ H⁺ + HCO₃^–.  Something like that, anyway.

** Though I have more sympathy for Scientism than most “isms”.

***Not to a mathematical certainty, but to such a high degree that there’s no clear point in considering other possibilities, pending new evidence and/or arguments.