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Proxy (climate)
 
 
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In climate
Climate

Climate encompasses the temperatures, humidity, atmospheric pressure, winds, rainfall, atmospheric particle count and numerous other Meteorology elements in a given region over long periods of time, as opposed to the term weather, which refers to current activity of these same elements....
 research, a proxy
Proxy (statistics)

In statistics, a proxy variable is something that is probably not in itself of any great interest, but from which a variable of interest can be obtained....
 variable is something that is probably not in itself of any great interest, but from which a variable of interest can be obtained. Temperature proxies such as tree ring widths and ice core
Ice core

An ice core is a core sample from the accumulation of snow and ice over many years that have re-crystallized and have trapped air bubbles from previous time periods....
 layering are used by climatologists to create a temperature
Temperature

In physics, temperature is a physical property of a Physical system that underlies the common notions of hot and cold; something that feels hotter generally has the greater temperature....
 record.

Examples include:

  1. Isotopic
    Isotope

    Isotopes are any of the different types of atoms of the same chemical element, each having a different atomic mass . Isotopes of an element have atomic nucleus with the same number of protons but different numbers of neutron....
     variations in ice core
    Ice core

    An ice core is a core sample from the accumulation of snow and ice over many years that have re-crystallized and have trapped air bubbles from previous time periods....
    s can be used to infer temperature changes and ice sheet volume.
  2. Beryllium 10
    Beryllium

    Beryllium is a chemical element with the symbol Be and atomic number 4.A Bivalent element, beryllium is found naturally only combined with other elements in minerals....
     variations can be used to infer past solar irradiance.
  3. Tree ring widths can be used to infer precipitation and temperature changes.


In all cases it is necessary to carefully calibrate the proxy against the variable of interest.






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In climate
Climate

Climate encompasses the temperatures, humidity, atmospheric pressure, winds, rainfall, atmospheric particle count and numerous other Meteorology elements in a given region over long periods of time, as opposed to the term weather, which refers to current activity of these same elements....
 research, a proxy
Proxy (statistics)

In statistics, a proxy variable is something that is probably not in itself of any great interest, but from which a variable of interest can be obtained....
 variable is something that is probably not in itself of any great interest, but from which a variable of interest can be obtained. Temperature proxies such as tree ring widths and ice core
Ice core

An ice core is a core sample from the accumulation of snow and ice over many years that have re-crystallized and have trapped air bubbles from previous time periods....
 layering are used by climatologists to create a temperature
Temperature

In physics, temperature is a physical property of a Physical system that underlies the common notions of hot and cold; something that feels hotter generally has the greater temperature....
 record.

Examples include:

  1. Isotopic
    Isotope

    Isotopes are any of the different types of atoms of the same chemical element, each having a different atomic mass . Isotopes of an element have atomic nucleus with the same number of protons but different numbers of neutron....
     variations in ice core
    Ice core

    An ice core is a core sample from the accumulation of snow and ice over many years that have re-crystallized and have trapped air bubbles from previous time periods....
    s can be used to infer temperature changes and ice sheet volume.
  2. Beryllium 10
    Beryllium

    Beryllium is a chemical element with the symbol Be and atomic number 4.A Bivalent element, beryllium is found naturally only combined with other elements in minerals....
     variations can be used to infer past solar irradiance.
  3. Tree ring widths can be used to infer precipitation and temperature changes.


In all cases it is necessary to carefully calibrate the proxy against the variable of interest. Tree growth, for example, is sensitive to precipitation and temperature as well as a number of other signals, and is often most sensitive during certain seasons of the year. Ice core proxies are usually the most direct.

Water isotopes and temperature reconstruction


Ocean water is mostly , with small amounts of and . In Vienna Standard Mean Ocean Water (VSMOW) the ratio of D to H is and O-18 to O-16 is . Fractionation occurs during changes between condensed and vapour phases: the vapour pressure of heavier isotopes is lower, so vapour contains relatively more of the lighter isotopes and when the vapour condenses the precipitation preferentially contains heavier isotopes. The difference from VSMOW is expressed as d18; and a similar formula for dD. d values for precipitation are always negative. The major influence on d is the difference between ocean temperatures where the moisture evaporated and the place where the final precipitation occurred; since ocean temperatures are relatively stable the d value mostly reflects the temperature where precipitation occurs. Taking into account that the precipitation forms above the inversion layer, we are left with a linear relation:

δ 18O = aT + b


which is empirically calibrated from measurements of temperature and d as a = 0.67 ‰/oC for Greenland
Greenland

Greenland is a member country of the Kingdom of Denmark located between the Arctic Ocean and Atlantic Oceans, east of the Canadian Arctic Archipelago....
 and 0.76 ‰/oC for East Antarctica
Antarctica

Antarctica is Earth's southernmost continent, overlying the South Pole. It is situated in the Antarctica of the southern hemisphere, almost entirely south of the Antarctic Circle, and is surrounded by the Southern Ocean....
. The calibration was initially done on the basis of spatial variations in temperature and it was assumed that this corresponded to temporal variations (Jouzel and Merlivat, 1984). More recently, borehole thermometry has shown that for glacial-interglacial variations, a = 0.33 ‰/oC (Cuffey et al., 1995), implying that glacial-interglacial temperature changes were twice as large as previously believed.

See also


  • Paleothermometer
    Paleothermometer

    A paleothermometer is a methodology for determining past temperatures using a Proxy_ found in a natural record such as a sediment, ice core, tree rings or TEX86....