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Fossil Pollen and Glacier Termini
Fossil pollen records have permitted
vegetation maps to be constructed of species distributions for various times in the past, and
tree rings have been used to determine the existence and geographical distributions of past major droughts.
Geographical distributions of pollen
from past periods can be compared with
climate conditions simulated for past periods by global climate models as checks
on the validity of such models. Glacial termini
(the farthest point down the mountain valley that a glacier extends) have been observed and
recorded by historical records and by the glacial deposits they leave behind.
Measurement of glacial termini reveal glacial retreat on all continents.
(Figure 4)
From these various proxy data, it should be apparent that a wealth of paleoclimate data are available to extend our record of the earth's surface temperature much farther back in time than the beginning of recorded temperatures.
