Pilot error, technical malfunction and bad weather are all possible causes checked by investigators.

Here are some seasonal pictures as western Siberia gets its debut whiteout of the autumn. 

230 wildfires rage in Russia’s coldest republic of Yakutia, with state of emergency declared in Krasnoyarsk and Irkutsk regions.

Challenge to polar doom warning from respected international expert Professor Peter Wadhams of Cambridge University.

Mi-8 delivered Hannah McKeand and Canadian companion to remote island weather station but crashed soon after, as pair abandon North Pole attempt.

Here we go back in time and remember 13 remarkable moments of 2013.

'Second Spring' arrives with rhododendron blossoming for rare encore in October.

These extraordinary pictures give graphic new evidence of climate change.

Average temperatures in the north of the Kara and Barents seas were 4C to 5C higher than previous years.

The freeze is so deep that horses - and even Rudolph - is brought indoors to warm up.