Game of Thrones Climatology
Sometimes scientists show their whimsical side by applying the tools of their profession to things outside the realm of science. Such was the case when a team of graduate students at the Department of Physics and Astronomy at Johns Hopkins University, decided to look into the oddly inconsistent seasons on the planet Westeros, the world invented by George R. R. Martin in A Game of Thrones. The group recently published a paper in which they explore the possible cause of summers lasting for years and winters for a generation. Using a numerical three-body computer simulation the intrepid researchers reach the conclusion that such a world is possible in the non-mythical universe.
Amidst all the hewing of limbs and hacking off of heads, faithful viewers of A Game of Thrones might reflect a bit on the truly unnatural seasons on Westeros. No clock like passing of time as on Earth, the seasons there seem to shift to summer for some unpredictable number of years, only to return to Ice Age like winter for a generation or more (or so the author implies). Most people take this strange climatological model as a given—this is, after all, a work of fantasy. But true to their science geek nature, a team of budding young scientists has written a paper outlining a possible astrophysical system that would explain such crazy climatology.
In “Winter is coming,” Veselin Kostov, Daniel Allan, Nikolaus Hartman, Scott Guzewich and Justin Rogers, launched an investigation to see if a world with the described characteristics was possible within the known laws of physics. They somewhat lyrically describe their quest:
Those that do not sow care little about such mundane things as equinoxes or planting seasons, or even crop rotation for that matter. Wherever and whenever the reavers reave, the mood is always foul and the nights are never warm or pleasant. For the rest of the good folks of Westeros, however, a decent grasp of the long-term weather forecast is a necessity. Many a maester have tried to play the Game of Weather Patterns and foretell when to plant those last turnip seeds, hoping for a few more years of balmy respite. Tried and failed. For other than the somewhat vague (if not outright meaningless) omens of “Winter is Coming”, their meteorological efforts have been worse than useless. To right that appalling wrong, here we attempt to explain the apparently erratic seasonal changes in the world of G.R.R.M. A natural explanation for such phenomena is the unique behavior of a circumbinary planet.
You will note that the investigators had to turn to a computer model to analyze their proposed star system, one in which a planet orbits a stellar binary comprised of two Sun sized stars. This is because, as any undergraduate can tell you, there is no analytic solution to the infamous three-body problem. They describe their methodology thus:
We simulate the orbit of the circumbinary planet (CBP) around a binary star composed of two Solar-type stars. We use a numerical three-body integrator in hierarchical Jacobian coordinates to calculate the position and velocity of the CBP at each point a long its orbit. The integrator starts when two stars and the planet are aligned along the same axis. It may be a choice of convenience, but we suspect it is portentous... The planet is dangerously close (but outside) the critical distance for dynamical stability. For simplicity, we assume the three bodies are coplanar, the mass of the planet is negligible and its axis is not tilted. At each time step, we compute the distance from the planet to the two stars and, using the black-body approximation, calculate the equilibrium surface temperature of the planet.
They posit that a circumbinary planet orbiting two 6000K, 1M⊙ stars in a ∼ 750-day orbit would provide climate variability similar to that found on Westeros. The lack of tilt of Westeros' axis is necessary, otherwise there would be other seasonal variation overlaying that caused by the inconstant irradiation from the pair of suns. The results of their simulation run are shown in the figure below, taken from the paper.
Still, other scientists remain skeptical. As reported in a news article in Science, Stephen Kane, an astronomer at the California Institute of Technology in Pasadena suggests a more “chaotic” system, for example a 3-star system, or a moon orbiting a gas giant. Still, this paper “is on the right path to providing a purely physical explanation” of the Westerosi seasons, he says. “Of course, if there's magic involved, all bets are off.” No sign of consensus here. But that is not the important message behind this paper.
Those who have frequented this Blog know that I have been highly critical of attempts to predict climate with computer models in the past. I remain so. However, this exercise bolsters my faith in future generations of scientists because these researchers have applied computer modeling properly. They were looking for insight, for a reason to believe that such a system was even possible. Indeed, they admit that their model is incapable of prediction the future of a specific reality such as Westeros.
“Thus, by speculating that the planet under scrutiny is orbiting a pair of Solar-type stars, we utilize the power of numerical three-body dynamics to predict that, unfortunately, it is not possible to predict either the length, or the severity of any coming winter,” they write.
Oh, would that our present day climate scientists admit their folly and confess the inadequacy of their models (now they have me writing that way). While this paper, to be published in the Oldtown Journal of Evil Omens, may be a tad facetious it nevertheless makes an important point: computer simulation is not reality.
Climate science has shown that computer models are not capable of predicting the future. Instead, it is climate science that has slipped into the realm of fantasy and make believe. Bear in mind that compared with the orbital model used in this study, the models with which climatologists attempt to divine the future climate of Earth are almost infinitely more complex. Climate science needs to admit defeat as did Kostov et al.:
Thus, by speculating that the planet under scrutiny is orbiting a pair of Solar-type stars, we utilize the power of numerical three-body dynamics to predict that, unfortunately, it is not possible to predict either the length, or the severity of any coming winter.
Kostov et al. conclude that, unfortunately, their “attempts to provide the good folks of Westeros with a reliable weather forecast are inconclusive”. They also mention that next they will turn their attention to the dragons, their carbon footprint and impact on climate in a subsequent paper. As the Starks will tell you, winter is coming to Westeros, as is a next glacial period to Earth, and neither will be denied. Certainly not by mythical factors such as dragons or anthropogenic global warming.
Be safe, enjoy the interglacial and stay skeptical.