Palaeotemperature reconstruction for the period of 20−18 ka BP in Siberia is based on δ¹⁸O analysis and ¹⁴C dating of large syngenetic ice wedges of yedoma exposures from Yamal Peninsula to Chukotka. The modern relationship between δ¹⁸O composition of ice-wedge ice and winter temperature reveals Palaeotemperature reconstruction. Snow meltwater is considered to be the main source of ice-wedge ice. In modern ice wedges during the last 60–100 years δ¹⁸O fluctuates are between −14 and −20‰ in western Siberia and between −23 and −28‰ in northern Yakutia. The trend in δ¹⁸O distribution in ice wedges dated at 20−18 ka BP is similar to the modern one. δ¹⁸O values in Late Pleistocene wedges are more negative going from the west to the east: from −19 to −25‰ in western Siberian ice wedges to −30 to −35‰ in northern Yakutia. At 20−18 ka BP mean January temperatures were about 8–12°C lower (in Chukotka up to 17–18°C) than at present.

Mean January air temperaures of the Siberian permafrost were compiled from Vasil'chuk 1992 with additions and amendments).Data were submitted and proofread by Yurij K Vasil'chuk and Lyubov Bludushkina at the faculty of Geography, department of Geochemistry of Landscapes and Geography of Soils, Lomonosov Moscow State University.