Extreme temperature events in summer in northwest Siberia since AD 742 inferred from tree rings

Frost and light rings of living and dead individuals of Siberian juniper (Juniperus sibirica Burgsd.) and Siberian larch (Larix sibirica Ledeb.) growing at the upper (Polar Ural Mountains) and polar (Yamal Peninsula) tree lines in northwest Siberia have been studied to reconstruct summer frosts and abrupt temperature declines during the second half of the growing season over the past 1250 years. The most severe temperature events in both regions were in AD 801, 1109, 1259, 1278, 1466, 1601 and 1783. Comparison of our data with data from other regions of the world shows that there is agreement in the timing of extreme temperature events in AD 800–801, 1109, 1258–1259, 1453, 1466, 1585, 1601, 1783, 1884, 1912 and 1992 between several regions. Most probably, these extremes have been caused by climatically effective explosive volcanic eruptions.