File:2000 Year Temperature Comparison.png
From Global Warming Art
This image is a comparison of 10 different published reconstructions of mean temperature changes during the last 2000 years. More recent reconstructions are plotted towards the front and in redder colors, older reconstructions appear towards the back and in bluer colors. An instrumental history of temperature is also shown in black. The medieval warm period and little ice age are labeled at roughly the times when they are historically believed to occur, though it is still disputed whether these were truly global or only regional events. The single, unsmoothed annual value for 2004 is also shown for comparison. (Image:Instrumental Temperature Record.png shows how 2004 relates to other recent years).
It is unknown which, if any, of these reconstructions is an accurate representation of climate history; however, these curves are a fair representation of the range of results appearing in the published scientific literature. Hence, it is likely that such reconstructions, accurate or not, will play a significant role in the ongoing discussions of global climate change and global warming.
For each reconstruction, the raw data has been decadally smoothed with a σ = 5 yr Gaussian weighted moving average. Also, each reconstruction was adjusted so that its mean matched the mean of the instrumental record during the period of overlap. The variance (i.e. the scale of fluctuations) was not adjusted (except in one case noted below).
Except as noted below, all original data for this comparison comes from  and links therein. It should also be noted that many reconstructions of past climate report substantial error bars, which are not represented on this figure.
|Temperature Record Series|
|This figure is part of series of plots showing changes in Earth's temperature over time.|
|Time Period: 25 yrs | 150 yrs | 1 kyr | 2 kyr | 12 kyr | 450 kyr | 5 Myr | 65 Myr | 500 Myr|
|See also: Future predicted changes | Map of recent warming | Temperature change category|
The reconstructions used, in order from oldest to most recent publication are:
- (dark blue 1000-1991):
- [abstract] [ Jones, P.D., K.R. Briffa, T.P. Barnett, and S.F.B. Tett (1998). "High-resolution Palaeoclimatic Records for the last Millennium: Interpretation, Integration and Comparison with General Circulation Model Control-run Temperatures". The Holocene 8: 455-471.
- (blue 1000-1980):
- [abstract] [ Mann, M.E., R.S. Bradley, and M.K. Hughes (1999). "Northern Hemisphere Temperatures During the Past Millennium: Inferences, Uncertainties, and Limitations". Geophysical Research Letters 26 (6): 759-762.
- (light blue 1000-1965):
- (lightest blue 1402-1960):
- [abstract] [ Briffa, K.R., T.J. Osborn, F.H. Schweingruber, I.C. Harris, P.D. Jones, S.G. Shiyatov, and E.A. Vaganov (2001). "Low-frequency temperature variations from a northern tree-ring density network". J. Geophys. Res. 106: 2929-2941.
- (light green 831-1992):
- (yellow 200-1980):
- [abstract] [ [ Mann, M.E. and P.D. Jones (2003). "Global Surface Temperatures over the Past Two Millennia". Geophysical Research Letters 30 (15): 1820.
- (orange 200-1995):
- [abstract] [ [ Jones, P.D. and M.E. Mann (2004). "Climate Over Past Millennia". Reviews of Geophysics 42: RG2002.
- (red-orange 1500-1980):
- [abstract] [ Huang, S. (2004). "Merging Information from Different Resources for New Insights into Climate Change in the Past and Future". Geophys. Res Lett. 31: L13205.
- (red 1-1979):
- [abstract] [ [ Moberg, A., D.M. Sonechkin, K. Holmgren, N.M. Datsenko and W. Karlén (2005). "Highly variable Northern Hemisphere temperatures reconstructed from low- and high-resolution proxy data". Nature 443: 613-617.
- (dark red 1600-1990):
- [abstract] [ Oerlemans, J.H. (2005). "Extracting a Climate Signal from 169 Glacier Records". Science 308: 675-677.
(black 1856-2004): Instrumental data was jointly compiled by the Climatic Research Unit and the UK Meteorological Office Hadley Centre. Global Annual Average data set TaveGL2v was used. Documentation for the most recent update of the CRU/Hadley instrumental data set appears in:
- [abstract] Jones, P.D. and A. Moberg (2003). "Hemispheric and large-scale surface air temperature variations: An extensive revision and an update to 2001". Journal of Climate 16: 206-223.
This figure was prepared by Robert A. Rohde from publicly available data.
- Data from Moberg et al. was taken directly from the supplemental information accompanying the Nature article.
- Data for Oerlemans was provided by William M. Connolley.
- Esper et al. reported only fluctuations in "arbitrary" units, so the variance in this record was rescaled to match the variance during the period of overlap with the instrumental record.
- When a paper included multiple reconstructions, the global annually average temperature data was used. If this was not reported, then Northern Hemisphere annually averaged data was used.
- Four records appearing at  were not used in preparing this graph for the following reasons:
- Mann et al. 98 was not included because Mann et al. 99 extended and updated that record.
- Briffa et al. 98 was not included because Briffa et al. 2001 extended and updated that record.
- Pollack et al. 98 was not included because the reported data was not found to be in a form that allowed for easy replotting.
- Mann et al. 2000 was not used because it did not included an original reconstruction covering at least the Northern Hemisphere.
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