Imagem:2000 Year Temperature Comparison.png

[edit] Description

Expansion of the last 1000 years

Temperature variations during the preceding 12000 years. Note that present day is placed at the left hand side

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).

For the purposes of this comparison, the author is agnostic as to which, if any, of the reconstructions of global mean temperature is an accurate reflection of temperature fluctuations during the last 2000 years. However, since this plot is a fair representation of the range of reconstructions appearing in the published scientific literature, 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 [1] 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.

[edit] Reconstructions

The reconstructions used, in order from oldest to most recent publication are:

1. (dark blue 1000-1991): P.D. Jones, 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.
2. (blue 1000-1980): M.E. Mann, 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.
3. (light blue 1000-1965): Crowley and Lowery (2000). Northern Hemisphere Temperature Reconstruction, Ambio, 29: 51-54. Modified as published in Crowley (2000). Causes of Climate Change Over the Past 1000 Years, Science, 289: 270-277.
4. (lightest blue 1402-1960): K.R. Briffa, T.J. Osborn, F.H. Schweingruber, I.C. Harris, P.D. Jones, S.G. Shiyatov, S.G. and E.A. Vaganov (2001). Low-frequency temperature variations from a northern tree-ring density network, J. Geophys. Res., 106: 2929-2941.
5. (light green 831-1992): J. Esper, E.R. Cook, and F.H. Schweingruber (2002). Low-Frequency Signals in Long Tree-Ring Chronologies for Reconstructing Past Temperature Variability, Science, 295(5563): 2250-2253.
6. (yellow 200-1980): M.E. Mann and P.D. Jones (2003). Global Surface Temperatures over the Past Two Millennia, Geophysical Research Letters, 30(15): 1820. DOI:10.1029/2003GL017814.
7. (orange 200-1995): P.D. Jones and M.E. Mann (2004). Climate Over Past Millennia, Reviews of Geophysics, 42: RG2002. DOI:10.1029/2003RG000143
8. (red-orange 1500-1980): S. Huang (2004). Merging Information from Different Resources for New Insights into Climate Change in the Past and Future, Geophys. Res Lett., 31: L13205. DOI:10.1029/2004GL019781
9. (red 1-1979): A. Moberg, 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. DOI:10.1038/nature03265
10. (dark red 1600-1990): J.H. Oerlemans (2005). Extracting a Climate Signal from 169 Glacier Records, Science, 308: 675-677. DOI:10.1126/science.1107046

(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 [2] was used.

Documentation for the most recent update of the CRU/Hadley instrumental data set appears in: P.D. Jones 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.

[edit] Copyright

The original version of this figure was prepared by Robert A. Rohde from publicly available data, and is incorporated into the Global Warming Art project.

[edit] Notes

1. Data from Moberg et al. was taken directly from the supplemental information accompanying the Nature article.
2. Data for Oerlemans was provided by William M. Connolley.
3. 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.
4. When a paper included mulitple reconstructions, the global annually average temperature data was used. If this was not reported, then Northern Hemisphere annually averaged data was used.
5. Four records appearing at [3] were not used in preparing this graph for the following reasons:
   1. Mann et al. 98 was not included because Mann et al. 99 extended and updated that record.
   2. Briffa et al. 98 was not included because Briffa et al. 2001 extended and updated that record.
   3. Pollack et al. 98 was not included because the reported data was not found to be in a form that allowed for easy replotting.
   4. Mann et al. 2000 was not used because it did not include an original reconstruction covering at least the Northern Hemisphere.

[edit] External references

• http://www.ncdc.noaa.gov/paleo/recons.html

[edit] Related Images

Comparison of several temperature graphs.

<noinclude>

English Wikipedia has the similar Template:

2000 Year Temperature Comparison.png