ScienceMaster - JumpStart - Paleoclimatology


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Paleoclimatology *

What Is Paleoclimatology

Paleoclimatology is the study of past climate. The word is derived from the Greek root "paleo-," which means "ancient," and the term "climate." Paleoclimate is climate that existed before humans began collecting instrumental measurements of weather (such as temperature from a thermometer, precipitation from a rain gauge, sea level pressure from a barometer, wind speed and direction from an anemometer). Instead of instrumental measurements of weather and climate, paleoclimatologists use natural environmental (or "proxy") records to infer past climate conditions. Paleoclimatology includes the collection of evidence of past climate conditions, as well as the investigation of the climate processes underlying these conditions.

Proxy data are data that paleoclimatologists gather from natural recorders of climate variability, for example, tree rings, ice cores, fossil pollen, ocean sediments, coral and historical data. By analyzing records taken from these and other proxy sources, scientists can extend our understanding of climate far beyond the 140-year instrumental record.
Tree Rings
Since tree growth is influenced by climatic conditions, patterns in tree-ring widths, density, and isotopic composition reflect variations in climate. In temperate regions where there is a distinct growing season, trees generally produce one ring a year, and thus record the climatic conditions of each year. Trees can grow to be hundreds to thousands of years old and can contain annually resolved records of climate for centuries to millennia.

Ice Cores
Located high in mountains and deep in polar ice caps, ice has accumulated from snowfall over many centuries. Scientists drill through the deep ice to collect ice cores. These cores contain dust, air bubbles, or isotopes of oxygen, that can be used to interpret the past climate of that area.

Photographer: Michael Van Woert, NOAA NESDIS, ORA

Fossil Pollen
Each species and genus of plants produces pollen grains that have a distinct shape. These shapes can be used to identify the type of plant from which they came. Since pollen grains are well preserved in the sediment layers that form in the bottom of a pond, lake or ocean, an analysis of the pollen grains in each layer tell us what kinds of plants were growing at the time the sediment was deposited. Inferences can then be made about the climate based on the types of plants found in each layer.

Ocean & Lake Sediments
Between 6 and 11 billion metric tons of sediment accumulate in the ocean and lake basins each year. Scientist drill cores of sediment from the basin floors. Ocean and lake sediments consist of materials that were produced in the lake/ocean or that washed in from nearby land. These materials (preserved tiny fossils and chemicals in the sediments) can be used to interpret past climate.

Corals
Corals build their hard skeletons from calcium carbonate, a mineral extracted from sea water. The carbonate contains oxygen and the isotopes of oxygen, as well as trace metals, that can be used to determine the temperature of the water in which the coral grew. These temperature recordings can then be used to reconstruct climate during that period of time that the coral lived.

Photographer: Dr. James P. McVey, NOAA Sea Grant Program

Historical Data
Historical documents contain a wealth of information about past climates. Observations of weather and climatic conditions can be found in farmers' logs, travelers' diaries, newspaper accounts, and other written records. When properly evaluated, historical data can yield both qualitative and quantitative information about past climate. For example, historical grape harvest dates have been used to reconstruct summer temperatures (April - September) in Paris from 1370 - 1879. [From Bradley, 1990]

*Text and images on this web page courtesy of NOAA

URL: http://www.noaa.gov/questions/question_020201.html

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