21 000 10 000
Pleistocene Late Glacial Holocene
Years before present Year
400 000 300 000 200 000 100 000 1500 1600 1700 1800 1900 2007
Atmospheric carbon dioxide (CO
320
2
)
concentrations (ppm)
Ice core analysis
280
Observations
240
200
Ice core analysis
4 0.5
Temperature variations (°C)
Reference Reference
period: 1950 period: 1961-1990
0
0.25
Observations
0
-4
-0.25
-8
Ice core analysis Multiple proxy reconstructions
-0.5
400 000 300 000 200 000 100 000 1500 1600 1700 1800 1900 2007
Years before present Year
Last Glacial Maximum
21 000 years ago
Repeated glaciations, ice ages, inter-
Little Ice Age
rupted by warmer interglacial periods
Sources: Global Change. Carbon Dioxide Information Analysis Center, Oak Ridge Na-
Barnola, J.-M., Raynaud, D., Lorius, C. and Barkov, N.I. (2003). Historical tional Laboratory, U.S. Department of Energy, Oak Ridge
CO
2
record from the Vostok ice core. In Trends: A Compendium of Data
on Global Change. Carbon Dioxide Information Analysis Center, Oak Ridge
Keeling, C.D. and Whorf, T.P. (2005). Atmospheric CO
2
records from sites in
National Laboratory, U.S. Department of Energy, Oak Ridge
the SIO air sampling network. In Trends: A Compendium of Data on Global
Change. Carbon Dioxide Information Analysis Center, Oak Ridge National
CRU (2007). CRUTEM3v dataset. Climate Research Unit, University of East An- Laboratory, U.S. Department of Energy, Oak Ridge
glia. http://www.cru.uea.ac.uk/cru/data/temperature [Accessed 5 May 2007]
Mann, M.E. and Jones, P.D. (2003). 2,000 Year Hemispheric Multi-proxy
Etheridge, D.M., Steele, L.P., Langenfelds, R.L., Francey, R.J., Barnola, Temperature Reconstructions, IGBP PAGES/World Data Center for Paleo-
J.-M. and Morgan, V.I. (1998). Historical CO
2
records from the Law Dome climatology Data Contribution Series #2003-051. NOAA/NGDC Paleoclima-
DE08, DE08-2, and DSS ice cores. In Trends: A Compendium of Data on tology Program, Boulder