Large ground warming in the Canadian Arctic inferred from inversions of temperature logs

The simultaneous functional space inversion applied for the first time to the set of precise temperature logs from 61 wells located between 60° and 82°N in northern Canada shows evidence of large ground surface temperature (GST) warming. These results include highest latitude locations of the well temperature profiles known in the Northern Hemisphere. There is strong evidence that GST warming started in the late-18th century and lasted until the 20th century. Simultaneous inversion of all well temperature data suggests that the cumulative ground surface temperature change over the past five centuries amounts to about 2°C significantly exceeding recent estimates from conventional climate proxies. This large GST warming is also present in other circumpolar locations in the Northern Hemisphere.