Paleoclimatologists gather proxy
data from natural recorders of climate variability such as tree rings, ice
cores, fossil pollen, ocean sediments, corals and historical data. By analyzing
records taken from these and other proxy sources, scientists can extend
our understanding of climate far beyond the 100+ year instrumental record.
Listed below are some widely used proxy climate data
To top of page...
documents contain a wealth of information about past climates. Observations
of weather and climatic conditions can be found in ship and 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.
above demonstrates how historical grape harvest dates were used
to reconstruct summer temperatures (April - September) in Paris
from 1370 - 1879. [From Bradley, 1990; based on data
from Le Roy Ladurie and Baulant, 1980.]
their hard skeletons from calcium carbonate, a mineral extracted
from sea water. The carbonate contains 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 when the coral
more about the study of corals please visit
plants produce pollen grains. Their distinctive shapes can be used
to identify the type of plant from which they came. Since pollen
grains are well preserved in the sediment layers 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.
more about fossil pollen, please visit the following:
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.
more about tree rings please visit the following:
in mountains and in polar ice caps, ice has accumulated from snowfall
over many millenia. 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.
more about ice cores please visit the following sites:
& Lake Sediments:
of 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 include tiny fossils and chemicals that are used
to interpret past climates.
more about ocean & lake sediments, please visit the following: