Most Game of Thrones fans are willing to suspend their disbelief when it comes to Westeros’s wonky weather. The continent’s seasons defy physics, lasting for years and changing without predictability—but, whatever, it’s a fantasy story. Fans who are also climate scientists, though, can’t stop hypothesizing.

“As a scientist, I’m intrigued to come up with a biogeochemical climate explanation for what’s happening in Westeros,” Peter Griffith, who works in the field of carbon cycle and climate, says with delightful sincerity. Thomas Douglas, an environmental chemist working on snow, ice, and permafrost characterization under the Department of Defense’s U.S. Army Cold Regions Research and Engineering Lab in Alaska, agrees. Fortunately, their training has led them to develop several fascinating theories about how Westeros’s climate may have evolved.

This is how climate scientists have fun—by advancing high-concept and ultimately meaningless thought experiments. And as evidenced by our last piece on the intersection of climate science and Game of Thrones, we think it’s fun, too. Spoiler alert: the following is pretty nerdy.

VOLCANIC ACTIVITY

“In Game of Thrones, volcanic eruptions caused the end of the Valyrian civilization. So we know the planet has undergone massive volcanic eruptions,” Griffith explains.

On Earth, he continues, “volcanic eruptions can cause mini-winters or years without spring.” Volcanoes eject sulphuric acid into the troposphere and stratosphere, which creates cloud layers that reflect sunshine before it can reach the planet. “It’s like putting a mirror into the high atmosphere,” Griffith says.

Once it’s up there, the acid easily spreads. Within two weeks of the Krakatoa eruption in Indonesia in 1883, for example, its volcanic spewings had already circled the globe—affecting temperatures in places as far away as England.

The Doom of Valyria bears some resemblance to the Krakatoa event. According to the Song of Ice and Fire books, the Fourteen Fires—the string of volcanoes that comprised the bulk of the Valyrian Peninsula—erupted with enough force to cause earthquakes and tidal waves. Similarly, the Krakatoa eruptions led to multiple devastating tsunamis, which compounded a death toll that ultimately climbed to more than 36,000.

In both scenarios, groups of islands disappeared, save for a few remaining volcanoes that continue to erupt today. In “present-day” Essos, travelers close to Valyria still report clouds of ash and glowing red skies. The continually shifting landscape at Krakatoa also keeps burping, with the most recent major eruption coming in 2008.

Douglas also believes volcanoes could be the major cause for Westeros’s capricious climate. He points to the Deccan Trap rock formations in India, which were caused by volcanic activity—the bulk of which happened about 66 million years ago, during eruptions that may have lasted for 30,000 years. “Some geochemists believe that the volcanic emissions that caused the Deccan Traps led to gas and particulates in the atmosphere that plunged Earth into winter for years,” Douglas explains. “So if there were volcanoes erupting every year or two, for 10 years, on or near Westeros, it could shroud them in winter for years on end.”

In the Song of Ice and Fire books, we learn only about the Valyrian eruptions—but, Griffith opines, “There’s a great big unknown planet out there that could have other regions with active volcanoes too.”

METEORITES AND ASTEROIDS

According to Douglas, some believe that the aftermath of the Deccan Trap explosions is what actually killed the dinosaurs here on Earth. But the prevailing theory attributes this extinction to fallout from an asteroid impact. “Asteroids can send a lot of dust up into the sky, which will cool the Earth for what could be multiple years,” Douglas explains. Asteroid impacts are rare, though, and the seasons on Game of Thrones do have some degree of predictability; they come and go, even if they don’t do so regularly.

But what if the planet’s orbit around its sun cut through an asteroid belt? “If the planet got whacked by a giant meteorite every 10 years, it would then have winter for several years,” he says. And the length of the winters would depend on the size of the meteorites.

We know of at least one non-planetary mass traveling relatively close to Westeros’s planet: the Red Comet. As an omen, it has a variety of interpretations. In Melisandre’s vision, “Darkness will fall heavy on the world. The stars will bleed. The cold breath of winter will freeze the seas. And the dead will rise in the north.” Sounds like there could be some ancient belief in a connection between meteors and deep winters.

According to Westerosi lore, the Long Night was a winter that lasted a generation, with a darkness so complete that people never saw daylight. This would certainly be strange for a world that otherwise experiences regular years—which we know is true for Westeros’s planet, because the people there celebrate naming days, or birthdays—and therefore regularly orbits a sun. It is highly unlikely that any part of the planet would face away from the sun for an entire generation—though this is not impossible. (See below.) Therefore, this complete darkness may instead have resulted from a sky full of dust.

Scientific explanations for how any living thing could survive a generation of darkness would require enough mental gymnastics to warrant another article (and would probably lead even the most dedicated scientist to throw up her hands and say, “Whatever, it’s magic”). Then again, if most people perished during the Long Night—especially those living in particularly extreme conditions north of the Wall—this could partly explain why the Night King’s army is so large.

MILANKOVITCH CYCLES

“These are really cool,” gushes Douglas. Here’s the briefest, simplest explanation: the attributes of Earth’s own rotation and orbit shift slightly over time, and in repeating cycles. These shifts have major effects on the Earth’s climate. To get a little more granular:

The shape of a planet’s orbital path is called its “eccentricity.” Ours is slightly elliptical; over the course of about 100,000 years, it grows slightly more elliptical and then shrinks again. When the Earth’s orbit is at its most elliptical, our seasons are more extreme than when the orbit is at its most circular.

Obliquity, or axial tilt, is why we have seasons to begin with. If you inserted a rod from the North Pole to the South Pole, you’d have to grab it and tilt it before you sent the Earth around the sun. That’s why the Northern Hemisphere is closer to the sun than the Southern Hemisphere during half of the year, and vice versa; it’s also why it’s hot in Australia during Christmas. The tilt fluctuates, however, between 22.1 degrees and 24.5 degrees, and it takes about 40,000 years to shift from one extreme to the other.

The shifts in a planet’s axial tilt will most affect the climates around the poles, since those areas receive different amounts of sunlight depending on obliquity. Notably, it’s the climate of Westeros—as opposed to Essos, a more southerly continent—that shifts so extremely during winter, particularly in the north. Further, the four known continents of Westeros’s planet all seem to be in the same hemisphere. The southernmost land masses are the hottest and most inhospitable, suggesting proximity to an equator. Therefore, it is possible that during the Long Night, unknown people in a Southern Hemisphere spent a generation in Margaritaville.

Finally: remember that tilted rod through the poles? It’s also swiveling, ever so slightly, in a circular fashion. This tilt precession, as it’s called, completes its cycle about every 25,000 years.

What does this all have to do with Game of Thrones? Well, in the early 20th century, Serbian mathematician Milutin Milankovitch calculated when, in the past, each of these cycles—eccentricity, obliquity, and precession—was at its most extreme point. He also determined, crucially, when all three extremes occurred at the same time. Then he correlated those points of confluence to Earth’s major Ice Ages. His work was largely ignored until 1976, when deep-sea sediment samples confirmed that all of the major climate shifts in the last 450,000 years do in fact correspond to the cycles mapped out by Milankovitch.

Therefore, as Douglas postulates: “You can imagine that if Westeros were on a planet for which these cycles were way faster or way stronger, then the continent could go in and out of extreme winter or summer on a decade-long scale. And you would have extreme seasonalities.” Moreover, the seasons wouldn’t be completely predictable to an untrained citizen of that planet, provided the length of each Milankovitch cycle varied—as Earth’s do.

OR IT’S JUST MAGIC

In an interview included in a 2011 book called Speaking of the Fantastic III, George R. R. Martin himself said this: “I have gotten a number of fan letters over the years from readers who are trying to figure out the reason for why the seasons are the way they are . . . I have to say, ‘Nice try, guys, but you’re thinking in the wrong direction.’ This is a fantasy series. I am going to explain it all eventually, but it’s going to be a fantasy explanation. It’s not going to be a science-fiction explanation.”

Still, the possibility that no actual science is at play in Westeros does not diminish the fun for Douglas. He’s eager to hear Martin’s explanation, whatever it is. At the mention of magic, though, Douglas does draw an interesting parallel. “Martin is a brilliant author who can bend the laws of physics and chemistry as much as he wants in his storytelling. But we on planet Earth can’t ignore science. We don’t have another option to explain how our climate functions.”

And in any case, isn’t science just fantasy explained? In medieval Europe, doctors believed illnesses were caused by demons and fairies. As late as 1895, a man in Ireland killed his wife because he believed she was a changeling—and that was during Milankovitch’s lifetime. In other words, perhaps even a magical explanation will ultimately have some science behind it, too. Give Samwell Tarly a chance to dive into those Citadel books and figure it out, won’t you, George?