Climate sceptics regularly work themselves into a lather dismissing mainstream climate science as fantasy – but for once they have a point.

A researcher at Bristol University has trained his powerful supercomputer not at predicting the earth's future climate, but on the fictional world of Middle Earth – the backdrop for JRR Tolkien's Lord of the Rings.

To reproduce Middle Earth's climate, Dr Dan Lunt, an expert on past climate change, traced one of Tolkein's famously detailed maps, and then effectively "scanned" that into the university's supercomputer.

"For a model to work, all you need is a map of where continents are, and how high the mountains are," Lunt says. The machines at the Advanced Computing Research Centre then crunched the weather patterns of Rohan, Mirkwood, and the rest of Tolkien's world for about six days, or roughly 70 years in the model.

According to Lunt's analysis, the climate around Mount Doom (where Frodo must take the evil ring of power to be destroyed) is like LA – hot, with the volcanic ash creating a similar effect to LA's infamous smog. Meanwhile the Shire, Frodo and Bilbo Baggins' peaceful neighbourhood, is most similar to Lincolnshire or Leicestershire in the UK.

The Shire's climate is also similar to that of Dunedin in New Zealand, he found, suggesting the director of the blockbuster Lord of the Rings trilogy Peter Jackson chose the wrong locations for filming. "They made a mistake by filming in the north island – they should've filmed in the south island," says Lunt.

Writing under the pen name of Radagast the Brown in a mock paper on the work, Lunt also suggests that:

• Ships sailing for the Undying Lands in the west set off from the Grey Havens due to the prevailing winds in that region.

• Much of Middle Earth would have been covered in dense forest if the landscape had not been altered by dragons, orcs, wizards etc. • Mordor had an inhospitable climate, even ignoring the effects of Sauron – hot and dry with little vegetation.

But there's a serious point to the exercise, says Lunt,:

"The serious side is that the climate models I used, and those [other models] out there, are actually based on our fundamental understanding of science, of fluid mechanics, fluid motion, the science of convection in clouds, radiation from the sun, and the science of biology. And because of that, they're not just tuned for the modern earth, they can simulate any climate."

Climate models are used to predict what might happen to future temperatures as we pump out carbon dioxide via our factories, cars and power plants, leaving greenhouse gases in the atmosphere at what the UN climate science panel said in September were "unprecedented" levels. The Bristol team fed into that IPCC report with models that largely match previous climate records, a match that "give us confidence in the [projections for] future", says Lunt.

Lunt, who undertook the work in his spare time, admits to being a bit of a Lord of the Rings fan. "I read them a few times as a child," he says, before pausing. "And a few times as an adult, I must confess."

His attention to detail is certainly precious: there are even translations of his paper for Dwarvish and Elvish readers.