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The Earth's average surface absolute temperature for the 1961–1990 period has been derived by spatial interpolation of average observed near-surface air temperatures from over the land, oceans and sea ice regions, with a best estimate of 14 °C (57.2 °F). [44] The estimate is uncertain, but probably lies within 0.5 °C of the true value. [44]
The geologic temperature record are changes in Earth's environment as determined from geologic evidence on multi-million to billion (10 9) year time scales. The study of past temperatures provides an important paleoenvironmental insight because it is a component of the climate and oceanography of the time.
In 1862, Lord Kelvin calculated the age of the Earth at between 20 million and 400 million years by assuming that Earth had formed as a completely molten object, and determined the amount of time it would take for the near-surface to cool to its present temperature.
That is, deposits laid down by volcanism or by deposition of sediment derived from weathering detritus (clays, sands etc.). This includes all its fossil content and the information it yields about the history of the Earth: its past climate, geography, geology and the evolution of life on its surface.
Based on calculations of Earth's cooling rate, which assumed constant conductivity in the Earth's interior, in 1862 William Thomson, later Lord Kelvin, estimated the age of the Earth at 98 million years, [10] which contrasts with the age of 4.5 billion years obtained in the 20th century by radiometric dating. [11]
It was only in the 20th century that paleoclimatology became a unified scientific field. Before, different aspects of Earth's climate history were studied by a variety of disciplines. [5] At the end of the 20th century, the empirical research into Earth's ancient climates started to be combined with computer models of increasing complexity.
The Mann, Bradley & Hughes 1998 (MBH98) multiproxy study on "Global-scale temperature patterns and climate forcing over the past six centuries" was submitted to the journal Nature on 9 May 1997, accepted on 27 February 1998 and published on 23 April 1998. The paper announced a new statistical approach to find patterns of climate change in both ...
(The same increment as the Celsius scale) Thomson's best estimates at the time were that the temperature of freezing water was 273.7 K and the temperature of boiling water was 373.7 K. [33] These two properties would be featured in all future versions of the Kelvin scale, although it was not yet known by that name.