Scientists have come up with a theory to explain the strange, extended seasons – where summer can last for years – in the world of hit fantasy drama Game Of Thrones.

The phenomenon could be explained by a so-called “tumbling” of the tilt of the spinning axis of the planet as it orbits the sun.

This could occur in such a way that the same hemisphere always tilts towards the sun, they suggest.

Researchers from the Universities of Bristol, Cardiff and Southampton used a model to simulate the climate of Game Of Thrones.

They found that The Wall – where the land of Westeros is guarded from the White Walkers - has a winter climate similar to that of Lapland in Finland.

Casterly Rock – the stronghold of the scheming Lannisters – has a climate similar to Houston, Texas, and Changsha in China.

Wind speeds and directions predicted by the climate model explain the dominance of the seas by the Iron Fleet and the likely attack plans of invading dragon hordes from Essos.

They also give an explanation for the trading routes between Westeros and the Free Cities across the Narrow Sea.

Temperatures predicted by the climate model indicate the likely hibernation zones of the White Walkers during the summer.

Professor Dan Lunt, of the University of Bristol’s School of Geographical Studies, said: “Because climate models are based on fundamental scientific processes, they are able not only to simulate the climate of the modern Earth, but can also be easily adapted to simulate any planet, real or imagined, so long as the underlying continental positions and heights, and ocean depths are known.”

The researchers also modelled the global warming that would occur if concentrations of greenhouse gases in the atmosphere were to be doubled, due to increases in carbon dioxide and methane emissions from dragons and excessive use of wildfire.

They estimate a warming of 2.1C for a doubling of carbon dioxide – the climate sensitivity of the world of Game of Thrones.

This is within the range of 1.5 to 4.5C predicted for the real world by the Intergovernmental Panel on Climate Change (IPCC).

Professor Carrie Lear, from Cardiff University, said: “This work is a bit of fun, but it does have a serious side. Climate models simulate real physical processes which operate in both cooling and warming climates.”

The full results of the Game of Thrones study have been published in a mock journal article, also available in Dothraki and High Valyrian – fictional languages from the show.

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Character Samwell Tarly, who is studying to become a “maester” at the Citadel in Oldtown in Westeros, is listed as the author of the research.

The actual model simulations were carried out on the supercomputers of the Advanced Centre for Research Computing at the University of Bristol.

They were not funded in any way and were set up in the researchers’ spare time.