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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.
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".
Proxies of global climatic significance are, however, less ambiguous in paleotemperature interpretation. Marine biota have offered by far the most proxies for paleotemperature, of which the microfossils, because of their widespread, abundance and sensitive to latitudinal changes, have provided many primary important paleotemperature indicators.
Paleoclimatology (British spelling, palaeoclimatology) is the scientific study of climates predating the invention of meteorological instruments, when no direct measurement data were available. [1] As instrumental records only span a tiny part of Earth's history , the reconstruction of ancient climate is important to understand natural ...
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).
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
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.
As of 2006, these uncertainties were considered too great to allow conclusion on whether the tree ring record diverges from other proxies during this period. [6] In more recent studies evidence suggested that the divergence is caused by human activities, and so confined to the recent past, but use of affected proxies can lead to overestimation ...