Abstract:
We review evidence for climate change over the past several millennia from
instrumental and high-resolution climate "proxy" data sources and climate
modeling studies. We focus on changes over the past 1 to 2 millennia. We
assess reconstructions and modeling studies analyzing a number of different
climate fields, including atmospheric circulation diagnostics, precipitation,
and drought. We
... devote particular attention to proxy-based reconstructions of
temperature patterns in past centuries, which place recent large-scale warming
in an appropriate longer-term context. Our assessment affirms the conclusion
that late 20th century warmth is unprecedented at hemispheric and, likely,
global scales. There is more tentative evidence that particular modes of
climate variability, such as the El Nino/Southern Oscillation and the North
Atlantic Oscillation, may have exhibited late 20th century behavior that is
anomalous in a long-term context. Regional conclusions, particularly for the
Southern Hemisphere and parts of the tropics where high resolution proxy data
are sparse, are more circumspect. The dramatic differences between regional
and hemispheric/global past trends, and the distinction between changes in
surface temperature and precipitation/drought fields, underscore the limited
utility in the use of terms such as the "Little Ice Age" and "Medieval Warm
Period" for describing past climate epochs during the last millennium.
Comparison of empirical evidence with proxy-based reconstructions demonstrates
that natural factors appear to explain relatively well the major surface
temperature changes of the past millennium through the 19th century (including
hemispheric means and some spatial patterns). Only anthropogenic forcing of
climate, however, can explain the recent anomalous warming in the late 20th
century.
The data files contain the raw and smoothed (i.e. as plotted) data for some of
the plots in Jones and Mann 2004. If the files are used in any paper, report or
other form of publication, then please acknowledge the Reviews of Geophysics
paper together with the specific original references to any series used.
Data for the series used in Figures 2, 4-7 and 8 are mostly available. Some
series are missing as we have been asked not to make these freely available.
For these, you will have to contact the appropriate author(s). For some, but
not all files, we have included the raw data together with the smoothed data
as plotted. Most of the series are in anomalies, from periods given in the
figure captions of the paper. Some series are only available as smoothed
versions and some raw series are scanned versions from the original papers
(i.e. also smoothed to varying degrees).
File contents:
Figure 2.
jonesmannrogfig2c.txt:
Instrumental temperature, 20-year smoothed annual average values for the
Northern Hemisphere (from HadCRUT2v), central Europe, Fennoscandia, and
central England.
Figure 4. Local and regional proxy temperature reconstructions by continent.
jonesmannrogfig4a.txt: Western North America
jonesmannrogfig4b.txt: North Atlantic
jonesmannrogfig4c.txt: Europe
jonesmannrogfig4d.txt: Eastern Asia
jonesmannrogfig4e.txt: Tropics
jonesmannrogfig4f.txt: Tasmania
Figure 5.
jonesmannrogfig5.txt:
Global/Hemispheric mean annual temperature reconstructions
Figure 6.
jonesmannrogfig6a.txt:
Reconstructions of the Southern Oscillation Index (SOI)
jonesmannrogfig6b.txt:
Reconstructions of the North Atlantic Oscillation (NAO)
Figure 7.
jonesmannrogfig7.txt:
Estimates of natural and anthropogenic radiative forcings over the last couple
of millennia used by climate models to simulate the climate
over the period.
Figure 8.
jonesmannrogfig8.txt: Model-based estimates of N. Hemisphere temperature
variations over the past two millennia.
jonesmann-nhrecon-rescale.txt:
Re-scaled Jones-Mann 2004 N.Hemisphere temperature reconstruction, to the same
decadal standard deviation as the instrumental record over the 1856-1995
period. 
