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

Figure 2. Fraction of the records with normalized values in given ranges
Fig. 2. Fraction of the records available in each year that have normalized values > 0 (red line), > 1 (light red shading), > 2 (dark red shading), < 0 (blue line), < -1 (light blue shading), and < -2 (dark blue shading), with the latter three series multiplied by -1 before plotting. The series are shown from 800 to 1995 and have been filtered to remove variations on time scales less than 20 years.
Vol. 311, Issue 5762, pp. 841 - 844
10 February 2006.

Timothy J. Osborn and Keith R. Briffa
Climatic Research Unit, School of Environmental Sciences, University of East Anglia, Norwich, UK

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 Little Ice Age, but comparison with instrumental temperatures shows the spatial extent of recent warmth to be of greater significance than that during the medieval period.
Download data from the WDC Paleo archive:
Northern Hemisphere Spatial Extent of Warm and Cold Conditions
in Text (415K) or Microsoft Excel (2.1MB) format.

To read or view the full study, please visit the Science website.
It was published in Science, Vol. 311, Issue 5762, 10 February 2006.
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