title: Comment on "The spatial extent of 20th-century warmth in the context of the past 1200 years".
abstract: Osborn and Briffa (Reports, 10 February 2006, p. 841) identified anomalous periods of warmth or cold in the Northern Hemisphere that were synchronous across 14 temperature-sensitive proxies. However, their finding that the spatial extent of 20th-century warming is exceptional ignores the effect of proxy screening on the corresponding significance levels. After appropriate correction, the significance of the 20th-century warming anomaly disappears.
authors.affiliation: Freie Universität-Berlin, Institut für Meteorologie, Carl-Heinrich-Becker-Weg 6-10, D-12165 Berlin, Germany. gerd.buerger@met.fu-berlin.de
authors.forename: Gerd
authors.initials: G
authors.lastname: Bürger