The Viking era came well before the Industrial Revolution — when humans began burning large amounts of fossil fuels which some scientists say causes global warming — and suggests that there are strong natural climate forces that have a profound effect on the extent of Arctic sea ice coverage. However, this is not a new theory — it was discussed as far back as the 19th century.
According to an 1887 newspaper article entitled “Variations in Climate,” Scandinavian Vikings were able to sail through the Arctic Ocean and establish colonies in the “highest north latitude” of Greenland and North America centuries before the arrival of Christopher Columbus. These colonies, however, were abandoned by the Vikings due to “the increasing cold.”