I don't think anyone's actually posted a link to the Leibman paper:
NEW PERMAFROST FEATURE – DEEP CRATER IN CENTRAL YAMAL
(WEST SIBERIA, RUSSIA) AS A RESPONSE TO LOCAL CLIMATE FLUCTUATIONSMarina O. Leibman, Alexander I. Kizyakov, Andrei V. Plekhanov,
Irina D. Streletskaya
ABSTRACT. This paper is based on field data obtained during short visits to a newly formed permafrost feature in a form of relatively narrow, deep crater. Excluding impossible and improbable versions of the crater’s development, the authors conclude that it originated from warmer ground temperatures and an increase in unfrozen water content, leading to an increase in pressure from gas emissions from permafrost and ground ice. This conclusion is also supported by known processes in the palaeo-geography of Yamal lakes and recent studies of gas-hydrate behavior and subsea processes in gas-bearing provinces.
CONCLUSIONS (1) An exciting permafrost feature, a gas emission crater surrounded by a parapet no more than 30 m in diameter is observed;
(2) As water accumulates at the bottom of the hole, the feature has no access to deeper layers and the assumption that deep-seated gas deposits caused the crater is implausible;
(3) No traces of human activity in the vicinity of the crater were found, so this phenomenon is of a purely natural origin;
(4) The date of the crater’s formation is estimated to have been in the late fall of 2013;
(5) The high concentration of methane in the hole, which decreases in the vicinity of the hole and is negligible far from the hole, indicates the role of methane in the formation of the crater;
(6) No high background radiation and no traces of extremely high temperatures, which would point to a gas explosion or an extraterrestrial object such as a meteorite were observed.
RUSSIAN ACADEMY OF SCIENCES No.04[v.07] 2014, GEOGRAPHY ENVIRONMENT SUSTAINABILITY pp 68 - 80
http://www.rgo.ru/sites/default/files/gi214_sverka.pdf(H/T Alexander Ač on Robert Scribbler's blog)