Geoscience Reference
In-Depth Information
five
Reading the Past
the earth's history topics
If you want to learn about nature, to appreciate nature, it is nec-
essary to understand the language that she speaks in.
Richard Feynman,
h
e Character of Physical Law
Archaeologists dig up clues left by ancient societies—bits of
broken pottery, bones, beads, chipped stones—by sit ing through ancient
garbage dumps and other remains of their daily lives. By methodically sit ing
through and analyzing the preserved remains, they can infer much about
past civilizations, their daily lives, and rises and falls. Similarly, paleoclima-
tologists learn about the earth's climatic history, including patterns of wet
and dry, warm and cold, by looking for clues buried in glaciers, trees, fossils,
corals, and sediments preserved in lakes, marshes, and the ocean.
To begin exploring what the natural climate archives have to tell us
about the past, it is necessary to introduce a few of the ways that earth
scientists decipher the clues of climate conditions in bygone eras. h e
story of the earth's ancient climate is not written in paper and ink: it is writ-
ten in sediment, stone, trees, ice, and other types of natural materials, wait-
ing to be uncovered, deciphered, and interpreted. Although the language
is not familiar to most humans, earth scientists have devised ways, using
increasingly advanced technology, to read and understand at least the basic
grammar.
Paleoclimatologists use whatever evidence they can i nd to piece together
past climate conditions, much like investigators at a crime scene. h ey search
for clues to the climate that may have existed in the past and to ways past
climate l uctuations may have af ected the environment, ecosystems, and past
human societies. Paleoclimate researchers have no access to direct records; no
one was measuring and recording the daily temperatures and rainfall during
prehistoric times. Instead, they use proxy—or indirect—evidence to assess
