They tell of repeated alternations between warm periods when the pass was useable and cold periods when it was shut by the ice.

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There is clear evidence that winter storms throughout southern Scandinavia were more frequent and intense during the multi-century Dark Ages Cold Period and the much more recent Little Ice Age than either now or other comparably warm periods.

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"The stalactites and stalagmites from these caves are a way of looking back in time to see how warm periods similar to our modern climate affect how far permafrost extends across Siberia, " said Dr Anton Vaks from the University of Oxford.

BBC: Siberian cave

During warm interglacial periods, when there may have been no sea-ice at all, an abundance of marine organisms would have left behind fossilised shells.

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Comparisons with other sites show that Homo erectus survived successive warm and cold periods in northern Asia.

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All the chemical and mineralogical evidence suggests that there have been no warm and wet periods in Martian history.

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