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 60degrees and. 82degreesN 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 2degreesC significantly exceeding recent estimates from conventional climate proxies. This large GST warming is also present in other circumpolar locations in the Northern Hemisphere. (C) 2004 Elsevier B.V. All rights reserved.