Twelve metres underground and nine degrees Celsius below zero, in a tunnel lined with ice, researcher Rosalia Ivanova is studying permafrost in Siberia, part of an effort to understand the destructive thawing occurring across the region. She works at the Permafrost Institute in Yakutsk, where ice cores -- some tens of thousands of years old -- are analysed. "Permafrost varies everywhere," she explains of a terrain that covers around 65 percent of Russia's territory. COMPLETES 42QM6WD + 433Q2WD IMAGES AND SOUNDBITES