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 Out of this emerged a view of the past climate based on limited data from tree rings, historical documents, sediments and other proxy data sources.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.
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 StudiesScientific References of StudiesAlthough 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:
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Several older reconstructions and animations: |
On to... "Climate before the last 2000 years"
Back to... "The Instrumental Record of Past Global Temperatures" |
http://www.ncdc.noaa.gov/paleo/globalwarming/paleolast.html Downloaded Thursday, 12-Feb-2009 09:42:50 EST Last Updated Friday, 17-Nov-2006 14:29:47 EST by paleo@noaa.gov Please see the Paleoclimatology Contact Page or the NCDC Contact Page if you have questions or comments. |