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Mysterious craters, with anomalously high concentrations of methane, have formed in the Yamal and Taymyr peninsulas of Siberia since 2014. While thawing permafrost owing to climate warming promotes methane releases, it is unknown how such release might be associated with explosion and crater formation. A significant volume of surface ice‐melt water can migrate downward driven by osmotic pressure associated with a cryopeg, a lens of salty water below. Overpressure reached at depth may lead to the cracking of the soil and subsequent decomposition of methane hydrates, with implications for the climate. Plain Language Summary: We show how osmosis drives explosions and methane release in Siberian permafrost. We anticipate that as well as being of direct relevance to permafrost researchers, this work will be of interest to a large number of people involved in climate change research, because the mechanism we uncover of osmotic pumping leading to permafrost explosions has potentially grave consequences involving the release of methane presently locked up in hydrates. Key Points: Surface ice‐melt water can migrate downward driven by the osmotic pressure associated with a cryopeg, a lens of salty water belowOverpressure can cause the frozen soil to crack resulting in mechanical explosion [ABSTRACT FROM AUTHOR]