For fans disappointed that the next series of Game of Thrones won’t be on our screens until 2019, here’s some food for thought: an attack on Westeros would be most likely to come from the south in winter and north in summer, according to a climate model of the world of Game of Thrones.

Furthermore, the model also sheds light on many mysteries surrounding the climate of the lands of Westeros and Essos – including the likely hibernation zones of White Walkers and the similarities between The Wall and Lapland.

You might well wonder why I and other climate science colleagues from Cardiff and Southampton universities have recently spent some of our spare time creating climate models of a fictional world.

Surface height of the Game of Thrones world. Illustration: Dan Lunt, University of Bristol

After all, is it helpful to know, as the model suggests, that due to the nature of the winds between Westeros and Essos, an attack on Westeros (whether by dragons, ships or both), would probably come via the south (from Dorne or Storm’s End) in winter, but more northerly (Vale of Arryn, or direct to King’s Landing), in summer?

And what of the revelation from the model that that the Iron Fleet’s naval prowess can be explained by very strong winds in the region of the Iron Islands? Or the knowledge that the temperatures predicted by the model indicate that in summer, the only places north of The Wall that are below freezing are the high-altitude regions of the Frostfangs, perhaps indicating the likely summer hibernation zones of White Walkers?

Apart from the fact that we found it fascinating to flesh out this fictional world with our model, it’s also a nice way to illustrate how climate models work and to highlight some fascinating climate science going on in the real world. For example, the SWEET project is currently using novel techniques to reconstruct the climate of super-warm states of Earth’s past – which in turn will help to test state-of- the-art climate models under conditions of high atmospheric carbon dioxide concentrations similar to those expected by the end of this century.

Illustration: Dan Lunt, University of Bristol

In our Game of Thrones model, by comparing the climate of places in the real world with those predicted by the model for the world of Game of Thrones, it could be seen that The Wall, where the land of Westeros is guarded from the White Walkers, has a climate in winter similar to that of Lapland. In contrast Casterly Rock, the stronghold of the scheming Lannisters, has a climate similar to that of Houston, Texas, and Changsha in China.



But how did we create the model in the first place? When carrying out this “work”, which is written up in the Philosophical Transactions of the Royal Society of King’s Landing and the Twitter account of @ClimateSamwell, the first step was to modify a “normal” climate model so that the land and ocean was laid out as in the maps provided by George RR Martin in the Game of Thrones books.

The northern hemisphere winter (top row a,b,c) and summer (bottom row (d,e,f)) in terms of surface temperature (◦C; left column) precipitation (mm/day; middle column) and surface pressure and winds (mbar; right column). Illustration: Dan Lunt, University of Bristol

The model was then modified to have the characteristic “extended seasons”, which the books and TV series describe as lasting several years. In the real world, the tilt of the spinning axis of the planet is at a fixed angle throughout the year, resulting in our characteristic four seasons. One way that seasons can be made to last longer is to allow this tilt of the spinning axis to change throughout the year, so that the Earth “tumbles” on its axis – a bit like a spinning top. If the Earth tumbles exactly once in a single year, then the spin axis always points towards (or away) from the sun, and the winter (or summer) is then permanent.

Configuration of Earth’s orbit for the ‘real’ Earth, in which the angle of tilt of the spinning axis of the Earth stays constant through the year. Illustration: Dan Lunt, University of Bristol

Interestingly, a very similar tumble – but occurring on much longer timescales of tens of thousands of years – causes major changes to the climate of our own planet. For example, 6,000 years ago it resulted in plants in the middle of what is today’s Sahara desert, and contributed to the ice age cycle that caused much of the UK to be covered in thick ice 20,000 years ago.

The world of the Game of Thrones, in which the tilt “tumbles” as the planet rotates round the sun, such that the angle of tilt changes, so that the same hemisphere always faces the sun, giving a permanent season. Illustration: Dan Lunt, University of Bristol

We also modelled the global warming that would occur if concentrations of greenhouse gases in the atmosphere were to be doubled, perhaps due to increases in CO2 and methane emissions from dragons and the excessive use of wildfire. The model estimates a global warming of 2.1C for a doubling of CO2 in the world of Game of Thrones.

The work illustrates that because climate models are based on fundamental scientific processes – many of which have been known since the days of Isaac Newton – they are able not only to simulate the climate of the modern Earth, but can also be easily adapted to simulate any planet past, present, future, or imagined, as long as the underlying continental positions and greenhouse gas concentrations are known.

Expected temperature change given a doubling of atmospheric carbon dioxide. Illustration: Dan Lunt, University of Bristol

Furthermore – and this is what I do in my “day job” – for some super-warm time periods in Earth’s past, there is geological data available that indicates what the climate actually was like, so we are able to test the climate models under high carbon dioxide conditions, similar to those we might expect by the end of this century if we continue emitting greenhouse gases at the current rate.

Such testing of climate models under super-warm greenhouse conditions is crucial if we are to have confidence in their predictions of the future – either for Earth or Westeros.

More tweets and the full range of climate gifs and media, can be found on Twitter @ClimateSamwell