And previous books have mentioned that the major castle in the north is built on or over some hot springs - presumably these springs along with the greenhouse might be capable of growing something during the winter.
But I’ll freely admit that that’s a bit of a fanwank.
And remember that even in the Summer, a lot of the North has snowfall. Westeros (just the continent itself) is around 3000 miles just from the Wall to the south shore of Dorne. And there’s still a lot of North beyond the Wall.
Unless the seasons don’t have anything to do with Westeros’ orbit around the sun. A year on Westeros could, like on earth, be the time it takes for it to go around the sun, which you could figure out by looking at things like the apparent motion of the stars, but that have nothing to do with the seasons, which come about for some entirely other reason.
A wizard did it was my first answer too. However. . . couldn’t Westros have a cycle of ice ages like Earth does, only faster. Instead of tens of thousands of years, it’s tens of years?
Leaving out magic, what could explain Westros’s climate. Even allowing for “winter”= Little Ice Age.
“Leaving out magic”? Why in that world would you do that? If dragons can fly, shadows kill people, ice zombies march, and prophesy come true, why should the weather be bound to only physics?
What could cause lengthy, unpredictable seasons?
A wizard. Magic. A curse upon the world until Balance is Restored. Conflict among all the Named and Unnamed Gods. There are some things Man was not meant to know. Plot.
I think he was asking if it would be possible for a planet to have seasons like that in the real world. I’m pretty sure, “Because that’s how the author wrote it,” had already occured to him.
According to either The Universe or How The Universe Works-- or Maybe If We Had No Moon, the only reason why earth has such stable seasons is because of our moon. Without it we’d wobble on our axis and not only would we have unpredictable seasons, we’d have unpredictable ice ages and waterworlds.
Tyrion was asked how many winters he’s seen, and he says 8 or 9 and the one he was born in was 3 years long.
Tyrion is under thirty and 3 years is an exceptional length for a winter, so most winters are probably two years or less. If we assume that a typical winter is a year long, that means you generally get two years of summer to grow food to prepare for it. Since the people of Westeros know about this, there could easily be gigantic underground granaries and storehouses. It is mentioned both at the wall and at the castles that there are huge stores of food.
As for the calendar, I assume it’s based on the path around the sun, since the maesters have observatories and keep detailed records so they can divine the start of winter.
The trouble is, as the story begins they are in the longest summer that anyone can remember, ten years long. Which means (if winters are half the length of the the summers) that five years of winter could be looming before them.
Assuming the planet is normal in composition, it could have a star that is undergoing a series of pulsations that lower the amount of energy the world gets. I don’t know why that would be, maybe magic.
Another possibility could be a cloud of small comets or asteroids that is orbiting the sun and every three years the planet goes through it and enough tiny comets hit the planet to start a nuclear winter for a year or so. Maybe the planet wouldn’t have much seasonal variations at all, but the cloud causes them. If the cloud isn’t uniform, if it has clumps of varying density, it could be why the duration of winter changes, or why for several years you can get no winter at all.
A year is the time it takes for a planet to go around the sun. Even in tropical areas on Earth where there is almost no seasonal variation, they still understand the concept of a year. Even places that have no winter can still measure years. Other variations in the climate can happen on an annual cycle even if the temperature doesn’t change much, in Hawaii it’s pretty much 80 degrees all year, but it’s dry from May to October and rainy from October to May.
So the world in “A Game of Thrones” has a regular year that is pretty much the same length as Earth’s year. It has regular winters and regular summers, even though they don’t call the part of the year when it gets cold and snows “winter”. Then every few years or decades it could be their Sun gets brighter or dimmer. When the sun is dimmer, they call that “winter”, because it’s much colder than a sidereal winter. But even during winter there might be a period warm enough to grow some crops. And it seems that in the South winter is much less intense. They have alligators there, a couple of years of freezing weather would kill them. So in the South it might not get below freezing very often even in winter.
The solar dimming doesn’t occur in a regular pattern, but there would be a lag–the hottest days of Earth-Summer occur after the summer solstice. So when the sun starts dimming, the temperatures don’t plunge right away, but slowly get colder. And when the sun brightens, you don’t get instant warmth, on Earth it takes months after the winter solstice for warm temperatures to return.
I agree that the long seasons are analogous to the Ice age/thaw cycle. In Westerosi terms we would be in the middle of a particularly long Summer, with the trend continuing toward warming. Each year has a cycle, but there are also groups of years that are warmer, or colder, or devastatingly dark and cold. Interesting that we never hear of a devastatingly hot Summer. There seems to be little chance of Dorne suffering blistering heat and drought. (Unless that’s what happened to Valyria?)
Two possibilities I’ve come up with:
The life cycle of the “Others” affects the weather. (“They come when it’s cold, or it gets cold when they come.”) I’m thinking like an important warming current which tempers the cold up North is interrupted by ice floes when they birth en masse or something. This does not, however, explain the legendary “Long nights” which occur during particularly long Winters.
An elliptical orbit complicated by a very large sister planet between them and their Sun. Although the Sun-spot theory above is also excellent, it wouldn’t allow for the predictions that the Maesters seem to be able to calculate. If the orbit itself accounted for a trend between longer/colder and shorter/warmer Winters, then the occaisional eclipsing of their sun by a larger planet with a closer orbit would create the kind of confusing unpredictibility they encounter. The rare total eclipse would account for the long Nights. This would require an extremely large and hot sun, very very far away, and rather longer years than we are accustomed to, making the Westerosi long-lived. (i.e. They marry at 14, but it takes 34 Earth years to be Westerosi 14.) That longevity might also explain their lack of ambition toward finding faster modes of travel.