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Reconstructions of global temperature of the past 2000 years, using composite of different proxy methods. In the study of past climates ("paleoclimatology"), climate proxies are preserved physical characteristics of the past that stand in for direct meteorological measurements [1] and enable scientists to reconstruct the climatic conditions over a longer fraction of the Earth's history.
Paleoclimatology uses a variety of proxy methods from Earth and life sciences to obtain data previously preserved within rocks, sediments, boreholes, ice sheets, tree rings, corals, shells, and microfossils. Combined with techniques to date the proxies, the paleoclimate records are used to determine the past states of Earth's atmosphere.
Global paleoclimate indicators are the proxies sensitive to global paleoclimatic environment changes. They are mostly derived from marine sediments.Paleoclimate indicators derived from terrestrial sediments, on the other hand, are commonly influenced by local tectonic movements and paleogeographic variations.
An important distinction is between so-called 'multi-proxy' reconstructions, which attempt to obtain a global temperature reconstruction by using multiple proxy records distributed over the globe and more regional reconstructions. Usually, the various proxy records are combined arithmetically, in some weighted average.
Frank, Esper & Cook (2007) "Adjustment for proxy number and coherence in a large-scale temperature reconstruction". Hegerl et al. (2007) "Detection of human influence on a new, validated 1500–year temperature reconstruction". Juckes et al. 2007 "Millennial temperature reconstruction intercomparison and evaluation".
Geochemical Climate Proxy: Ratio of Oxygen-18 to Oxygen-16 in calcite from deep sea sediment, and coral cores More Oxygen-18 = colder climatic periods Mass Spectrometer: ca 542,000,000 yrs BP Beryllium-10 Analysis Geochemical Climate Proxy: Ratio of Beryllium-10 to daughter isotopes in dust from ice cores
Reconstruction of the past 5 million years of climate history, based on oxygen isotope fractionation in deep sea sediment cores (serving as a proxy for the total global mass of glacial ice sheets), fitted to a model of orbital forcing (Lisiecki and Raymo 2005) [2] and to the temperature scale derived from Vostok ice cores following Petit et al. (1999).
The problem of changing response of some tree ring proxies to recent climate changes was first identified through research in Alaska conducted by Gordon Jacoby and Rosanne D'Arrigo. [ 3 ] [ 4 ] Keith Briffa 's February 1998 study showed that this problem was more widespread at high northern latitudes, and warned that it had to be taken into ...