The Spatial Extent of 20th-Century Warmth in the Context of the Past 1200 Years

@article{Osborn2006TheSE,
  title={The Spatial Extent of 20th-Century Warmth in the Context of the Past 1200 Years},
  author={Timothy J. Osborn and Keith R. Briffa},
  journal={Science},
  year={2006},
  volume={311},
  pages={841 - 844}
}
Periods of widespread warmth or cold are identified by positive or negative deviations that are synchronous across a number of temperature-sensitive proxy records drawn from the Northern Hemisphere. The most significant and longest duration feature during the last 1200 years is the geographical extent of warmth in the middle to late 20th century. Positive anomalies during 890 to 1170 and negative anomalies during 1580 to 1850 are consistent with the concepts of a Medieval Warm Period and a… 
Comment on "The Spatial Extent of 20th-Century Warmth in the Context of the Past 1200 Years"
TLDR
Osborn and Briffa identified anomalous periods of warmth or cold in the Northern Hemisphere that were synchronous across 14 temperature-sensitive proxies, but their finding that the spatial extent of 20th-century warming is exceptional ignores the effect of proxy screening on the corresponding significance levels.
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Response to Comment on "The Spatial Extent of 20th-Century Warmth in the Context of the Past 1200 Years"
Reconsidering the basis for selecting proxy records according to their correlation with local temperature has no substantive influence on the statistical significance of 20th-century warming that we
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