There is so much plot in
George R.R. Martin's A Song of Ice and Fire, so many mysteries and character arcs and secret Targaryen babies, that many of us have essentially forgotten the premise of this fantasy world. But there is one major thing that sets Westeros apart from the hundreds of other Middle-Earth clones out there, and that's the seasons. The seasons are super weird. Summers and winters last for years, and there's no way of predicting when the season will change. Legend even tells of the "Long Night," a winter that lasted for an entire generation. But why are the seasons like this in the first place? We may not know for sure, but that hasn't stopped fans from speculating wildly. Here are some of the top theories on the seasonal weirdness in A Song of Ice and Fire, from the scientifically plausible to the utterly bizarre.
Perhaps the most frustrating thing about this season business is that George R.R. Martin has promised that
he'll explain it all at the very end of the series. So, knowing Martin's writing pace, you shouldn't get your hopes up about solving this mystery any time soon.
Until then, though, we have plenty of working theories on why exactly winter is coming:
Some very dedicated grad students at the
Johns Hopkins Department of Physics and Astronomy have suggested that "such phenomena is the unique behavior of a circumbinary planet." Or, more simply, the seasons are out of whack because the Westeros planet has two suns. The double orbit of two suns could create erratic seasons of varying length, and the concept of a planet orbiting more than one star isn't too far-fetched. The idea of only one sun being visible at a time seems a little convenient, but it's still a plausible theory... except that some maesters believe that the seasons used to be normal. The double star system would mean that the seasons had always been weird.
There are several hints in the books that the seasons were once far shorter, and more predictable in length. After all, the people of Westeros do have the concept of a regular year. And in Essos, they have a myth about a second moon that once hung in the sky alongside the first. However, this moon came too close to the sun and it cracked open, releasing dragons into the world. This could be the mythologized version of an actual astronomical event: perhaps a second moon did break apart, showering the planet with meteors and messing with its tides, its orbit, and the cycle of the seasons.
The planet is too wobbly
The only reason that we have seasons here on Earth is that our planet is crooked. We have an axial tilt, meaning that as we travel our annual path through space, part of the globe leans closer or farther away from the sun depending on the time of year. If the Song of Ice and Fire planet had a wobbly,
unpredictable axial tilt, that might account for the odd seasonal changes—basically, they would have a mini ice age every couple of years. Even Earth has cycles of shifting axial tilt and variable orbit, called a Milankovitch Cycle. The only real question is... why would the axial tilt be so unstable? Is the planet a funky shape or something? Answer us, George.
Old Valyria was the home to the dragon lords and their dragons—until the whole peninsula blew up in the Doom of Valyria. We don't know exactly what happened in this cataclysm, but Valyria was supposedly built on a ring of volcanoes, so... probably volcanoes happened.
A big volcanic eruption can actually affect temperatures on the other side of the globe, so if the Doom was dramatic enough, it might have been able to plunge the world into an extended period of winter... but unless other volcanoes are erupting on the other side of the planet all the time, it probably wouldn't be enough to permanently wreck the seasonal cycle.
Humans screwed it all up by using too much magic
At the end of the day, A Song of Ice and Fire is a fantasy series, and GRRM has basically promised us that
the explanation of the seasons is going to be magical—not scientific. So what if humans went a little overboard with the magic? We know that magic in the ASOIAF universe always has a price, and the Valyrians went bonkers using magic to build their cities and perhaps even create their dragons. The Doom of Valyria might have been the result of an overambitious spell gone wrong, or maybe years of magic use and mining under volcanoes had taken its toll on the environment... just replace the dragons with fracking and SUVs, and the messed up seasons are basically magical global warming.
It's all the White Walkers' fault
We don't know much about the White Walkers, but we do know that they like it cold. Trying to make it winter all the time forever sure seems like
something the White Walkers would do. Perhaps they're somehow causing the wacky seasons by refusing to stay up north. Perhaps the creation of the White Walkers is what made the magical balance of Westeros to go haywire in the first place. Perhaps, with the Doom of Valyria knocking out the "fire" center of the world, the "ice" center of the world has been allowed to gain power unchecked for hundreds of years now.
There's an invisible god war going down
OK, so I doubt we'll see any gods in the
flesh in A Song of Ice and Fire, but... we've seen people brought back from the dead by both fire priests and White Walkers. It seems pretty clear that there's some iota of truth to the R’hllor religion, so maybe the seasonal strife is a reflection of some behind the scenes, divine war between the Lord of Light and the Great Other, in which people are mere pawns.
Or... y'know, it's the distant future on Earth and the Long Night was some kind of nuclear winter. Or Bran went back in time and left the fridge open. Or we'll just have to wait for book seven and find out for ourselves.