Global Surface Temperatures over the Past Two Millennia

Fig. 2a,b. Hemispheric temperature reconstructions.
Fig. 2a,b. Hemispheric temperature reconstructions.
Global Surface Temperatures over the Past Two Millennia
Geophysical Research Letters
Vol. 30, No. 15, 1820, August 2003
doi: 10.1029/2003GL017814

Michael E. Mann1 and
Philip D. Jones2.

1 Department of Environmental Sciences,
University of Virginia, Charlottesville VA, USA

2 Climatic Research Unit, University of East Anglia, Norwich, UK

We present reconstructions of Northern and Southern Hemisphere mean surface temperature over the past two millennia based on high-resolution 'proxy' temperature data which retain millennial-scale variability. These reconstructions indicate that late 20th century warmth is unprecedented for at least roughly the past two millennia for the Northern Hemisphere. Conclusions for the Southern Hemisphere and global mean temperature are limited by the sparseness of available proxy data in the Southern Hemisphere at present.

Download the reconstruction series from the WDC Paleo archive:
Hemispheric Temperature Reconstructions

Some of the individual proxy data series and paleoclimatic reconstructions used in this study are also available from the WDC Paleo archive:
Yang et al. 2002 China Temperature Reconstruction
Cronin et al. 2003 Chesapeake Bay Temperature Reconstruction
Cook et al. 2000 Tasmania Temperature Reconstruction
Quelccaya Peru Ice Core Data

Additional Climate Reconstructions can be obtained at WDC Paleo.

Locations of proxy data or reconstructions mentioned in this study:

Comparison of published reconstructions (Figure 1. from Mann et al. EOS Forum 2003):
Figure 1. Comparison of proxy-based NH temperature reconstructions [Jones et al., 1998; Mann et al., 1999; Crowley and Lowery, 2000] with model simulations of NH mean temperature changes over the past millennium based on estimated radiative forcing histories [Crowley, 2000; Gerber et al., 2002--results shown for both a 1.5°C/2*CO2 and 2.5°C/2*CO2 sensitivity; Bauer et al., 2003). Also shown are two independent reconstructions of warm-season extratropical continental NH temperatures [Briffa et al., 2001; Esper et al., 2002] and an extension back through the past two thousand years based on eight long reconstructions [Mann and Jones, 2003]. All reconstructions have been scaled to the annual, full Northern Hemisphere mean, over an overlapping period (1856-1980), using the NH instrumental record [Jones et al., 1999] for comparison, and have been smoothed on time scales of >40 years to highlight the long-term variations. The smoothed instrumental record (1856-2000) is also shown. The gray/red shading indicates estimated two-standard error uncertainties in the Mann et al. [1999] and Mann and Jones [2003] reconstructions. Also shown are reconstructions of ground surface temperatures (GST) based on appropriately areally-averaged [Briffa and Osborn, 2002; Mann et al., 2003] continental borehole data [Huang et al., 2000], and hemispheric surface air temperature trends, determined by optimal regression [Mann et al., 2003] from the GST estimates. All series are shown with respect to the 1961-90 base period.

To read or view the full study, please visit the AGU website.
It was published in Geophysical Research Letters, Vol. 30, No. 15, 1820, August 2003 doi: 10.1029/2003GL017814

M.E.M. acknowledges support for this work by the NSF and NOAA-sponsored Earth Systems History (ESH) program (NOAA award NA16GP2913). P.D.J. acknowledges support of the Office of Science (BER), U.S. Dept. of Energy, Grant No. DE-FG02-98ER62601.

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14 August 2003