An extreme storm may have contributed to the deaths of famed climbers George Mallory and Andrew Irvine as they tried to reach Everest's summit in 1924.

That is the conclusion of a new study using weather data recorded during their historic expedition.

Mallory and Irvine were sighted on 8 June 1924, scaling Everest's north-east ridge, before vanishing.

The storm caused a pressure drop big enough to deprive the climbers of oxygen, the new study proposes.

The research, published in the journal Weather, focuses on meteorological measurements from the 1924 expedition, which the authors uncovered at the Royal Geographical Society library in London.

Although the data were published as a table in a 1926 report on the expedition, they were never analysed for information on the disappearance of Mallory and Irvine until this study.

The researchers analysed barometric pressure measurements and found that during the Mallory and Irvine summit attempt, there was a pressure drop at Everest base camp of approximately 18 millibars (mbar).

Lead author GW Kent Moore, from the University of Toronto, Canada, described this as "quite a large drop".

He said: "We concluded that Mallory and Irvine most likely encountered a very intense storm as they made their way towards the summit."...