“Winter is coming” has been the tagline of Game of Thrones and endless Ned Stark memes across the internet, but outside the Seven Kingdoms and George R.R. Martin’s imagination, could our planet really survive that many years of winter?
Never mind that this is physically impossible. If we were hypothetically thrown into a winter that didn’t thaw out for years, the effects on our planet would depend on what caused the very thing Ned was dreading (besides the Night King blasting everything with ice). Earth’s orbit would only need to drop as far back as Mars, which is a freezing desert. That isn’t happening. Neither is a scenario where Earth just stops orbiting in winter—but say it did.
During the winter months, the northern hemisphere tilts away from the sun’s light and heat, which is why what would have been a rainstorm in July ends up being a blizzard in January. Earth suddenly stopping in orbit during the colder months would literally freeze its position like that. Meaning, any of us in the north would have to get our IKEA rug furs out like Jon Snow and brave years of shorter days, longer nights and frequent snowstorms. Without enough heat to melt it, the snow would keep accumulating.
Endless gloom and snow would shake the ecosystem after a few years. Maybe we wouldn’t get ice zombies, but things would start dying off. Many animals rely on deciduous trees and other plants that thrive during the spring and summer for food. If spring never came, neither would anything to eat, and as the herbivores started to vanish, so would the carnivores. Omnivores like bears (and humans) would probably hold out longer, but no species would be entirely safe from a weather forecast of nothing but temperatures hovering around zero.
Some creatures cheat the cold by lowering their metabolic rates and hibernating. While hibernation is a temporary way out if winter went on for a few more months, even this wouldn't last long enough to compete with years of snow and ice. The animals would end up either starving to death or poisoned by the toxic levels of metabolic waste products that accumulated during that deep sleep. Not many flora and fauna would emerge from such a winter alive, and some could even go extinct.
At least winter ends in Westeros—but what if it didn’t? Almost everything alive, except maybe a tardigrade, would face extinction. We’d be plunged into an ice age that would cover entire cities and even continents in mammoth ice sheets and glaciers. If anything edible survived, humans would have to ditch the supermarket and learn to hunt. Earth would be an ice giant in several hundred thousand years.
In other words, Earth is way better off as a “sweet summer child”.