Post-glacial climatic change and variability - The Global Climate System: Patterns, Processes, and Teleconnections - page 181

Table 6.1 Examples of major proxy methods to determine detailed past climate change and variability, their benefits and limitations

Proxy method Definition Spatial extent Time scale Benefits Limitations

Ice cores (O 18 ,
gases, dust)

Cored ice from ice
caps and glaciers

Greenland,
Antarctica, some
high-altitude and
high-latitude
glaciers

Several
100 000
years

Long records over
multiple millennia
Wide range of
information possible
Annual/seasonal analysis
possible

Small area of Earth's surface
Cold climates only
Detailed dating can be imprecise
Accuracy reduced with depth
Affected by changes in moisture
Affected by rate of horizontal flow

Dendrochronology Width and density
of tree-rings

Poleward of 30 8
where cold
season stops
growth

Up to about
10 000
years

Details about
temperatures and
moisture
Correlates well with
measured data
Potential for O 18 and
C 14 analysis
High-quality data record

Limited to high elevations or
mid to high latitudes
Limited to trees with annual
growth rings
Dependent on growing season
months
Highly dependent on
standardization method
Calibration only where
cross-dating possible

Coral Growth rings and

chemistry from
tropical coral
massives

Tropics with
shallow seas

Several
hundreds
of millennia
possible

Tropical complement
to tree-rings
Can provide precise dating
Continuous sampling
possible
Provide teleconnection
details (ENSO)
Detailed isotope and
elemental chemistry
analysis

Tropics only
Limited spatial distribution
Long records are rare
Strong dependence on water
temperature and salinity
Less accurate with depth
Seasonal cycle dominates