Paleoclimate Proxies

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Paleoclimate Proxies
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What is Paleoclimatology?

• The study of past climates prior to the
  instrument record.
• Scientists use indirect evidence (data) during
  past time periods to determine the climate at
  that time period.
• These climate imprints are referred to as
  proxies.

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Why Study Past Climates?

• It may help us to understand natural climate
  changes.
• The study of past climates may give us
  information into future climate scenarios.

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Why Study Climate?
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How do scientists study climate?
Satellites
Historical Proxy Records
Ancient Proxy Records
Instrument Record
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Climate History

• The instrument record extends back about 150
  years (1860).
• Since that time Earths temperature has increased
  0.7 C (1.3 F).
• In the past, climates were sometimes much colder
  than today.
• At other times they were much warmer than today.

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Historical Records

• Weather and climate observations can be found in
  ships logs, farmers diaries, newspaper accounts,
  and other written records.

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Sediment Cores

• Sediment cores can be taken from lakes, the
  shallow ocean, or the deep ocean.
• In some cases the thickness of these layers can
  be used to infer past climate.
• In other cases, these layers are composed of
  organic material that can be analyzed for other
  climate proxies.

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Pollen

• Pollen grains are well preserved in lake and
  ocean sediment.
• The analysis of each of these sediment layers
  provides information on the vegetation present at
  that time.
• Scientists can infer past climates (warm or cold)
  based on the distribution and changes in plant
  species.

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Stable Isotopes

• The most common element used in climate studies
  is oxygen.
• The isotopes of oxygen are
• O18 (rare)
• O17
• O16 (common)
• The ratio of O18 to O16 is affected by
  temperature and can be used as a climate proxy.

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Coral Reefs

• Corals are composed of calcium carbonate.
• This carbonate contains isotopes of oxygen that
  can be used to determine the water temperature
  when and where the corals grew.

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Ice Cores

• As snow and ice accumulate in polar glaciers a
  paleoclimate record accumulates of the
  environmental conditions of the time of
  formation.
• Ice cores can analyzed using stable isotope
  approaches for water or air bubbles within the
  ice as a record of past atmospheric
• gas concentrations.

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Tree Rings

• Tree growth is influenced by climate. These
  patterns can be seen in tree ring width and
  isotopic composition.
• Trees generally produce one ring each year.
• Trees ring records can extend back to the last
  1000 years.

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Conclusions

• All of these examples used individually or
  together can help piece together the past climate
  of a particular time period or region.