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Paleoclimatic Data for the Last 2000 Years

Beginning in the 1970's, paleoclimatologists began constructing a blueprint of how the Earth's temperature changed over the centuries before 1850 and the widespread use of thermometers. Out of this emerged a view of the past climate based on limited data from tree rings, historical documents, sediments and other proxy data sources. Today, many more paleoclimate records are available from around the world, providing a much improved view of past changes in the Earth's temperature.

Over the last decade, there has been a major breakthrough in our understanding of global temperature change over the last 1000 years. Several different but important studies, published in peer-reviewed scientific journals, revolutionized what we know about the 20th century in the context of past centuries. The research of the late 1990s formed the foundation for a progression of studies that followed, incorporating advances in statistical techniques and information from a broad range of proxy data types.
  • Northern Hemisphere Annual Temperatures from High-Resolution Proxy Data, AD 200-1995, Jones and Mann 2004
  • Northern Hemisphere Annual Temperatures from Low- and High-Resolution Proxy Data over the last 2000 Years, Moberg et al. 2005
  • The Spatial Extent of Northern Hemisphere Temperature Anomalies, AD 800-1995, Osborn and Briffa 2006
These studies are summarized below, and these and other studies are described in the 2006 report by the National Research Council titled "Surface Temperature Reconstructions for the Last 2,000 Years"

Modeling of past climates is an important and complementary area of research. These studies support the results of the proxy-based reconstruction and, more importantly, examine the contribution of higher greenhouse gas concentrations to Global Warming.

Summary of Proxy Temperature Studies

Scientific References of Studies

Although each of the proxy temperature records shown below is different, due in part to the diverse statistical methods utilized and sources of the proxy data, they all indicate similar patterns of temperature variability over the last 500 to 2000 years. Most striking is the fact that each record reveals a steep increase in the rate or spatial extent of warming since the mid-19th to early 20th centuries. When compared to the most recent decades of the instrumental record, they indicate the temperatures of the most recent decades are the warmest in the entire record. In addition, warmer than average temperatures are more widespread over the Northern Hemisphere in the 20th century than in any previous time.

The similarity of characteristics among the different paleoclimatic reconstructions provides confidence in the following important conclusions:
  • Dramatic warming has occurred since the 19th century.
  • The recent record warm temperatures in the last 15 years are indeed the warmest temperatures the Earth has seen in at least the last 1000 years, and possibly in the last 2000 years.
For a larger version of this graphic, please click here or on the graph
Image of last 2000 years

Several older reconstructions and animations:
On to... "Climate before the last 2000 years"
Back to... "The Instrumental Record of Past Global Temperatures"

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