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Figure 2c from Mann and Jones (2003),
Global surface temperatures over the past two millennia
GEOPHYSICAL RESEARCH LETTERS, VOL. 30, NO. 15, 1820.
Caption: Hemispheric temperature reconstructions (‘standard reconstructions’ based on area and local correlation weighting, shown as thick blue). All series are anomalies based on 1961–1990 instrumental reference period (mean shown by dashed line), and smoothed with a 40 year lowpass filter. Smoothed instrumental series are shown by thick red curve (the constraint employed by the filter preserves the late 20th century trend). 95% confidence intervals for the standard reconstructions are shown by yellow shading. .. (c) global mean (average of NH and SH) surface temperature reconstruction.