Page 231 - Earth's Climate Past and Future

PART IV

Deglacial Climate Change

The ability to reconstruct regional climate responses among different archives. These oscillations require an
across Earth’s entire surface also gives scientists the explanation other than orbital forcing, but their cause
opportunity to look at climate change from a geographic is as yet unknown.

perspective. Mapping climate changes at specific times In this part we address the following important
(“time slices”) gives researchers insights into specific questions:
regional processes that alter climate and allows
• To what extent does the timing of ice melting in the
comparisons of data with model simulations. Boundary
last 21,000 years support the Milankovitch theory that
conditions based on observations from the geologic
ice sheets are forced by orbital insolation?
record can be used to run model simulations of past
• What does the cooling of the tropics at the glacial
climates, and the results (output) from these simulations
maximum tell us about Earth’s sensitivity to the
can be compared with independent geologic data concentration of atmospheric CO ?
2
assembled into map form. The major boundary
• To what extent do changes in tropical moisture during
conditions that have driven climate changes during the the last 21,000 years support the Kutzbach theory that
last 21,000 years have been changes in the size of ice orbital insolation controls the strength of summer
sheets, in seasonal insolation, and in the levels of monsoons?
greenhouse gases in the atmosphere (Chapter 13). • How has Earth’s climate system responded to
In climate archives with sufficiently high resolution, insolation changes during the several thousand years
since the ice sheets melted?
climatic oscillations lasting thousands of years are
apparent, especially in and around the North Atlantic • What is the origin of the brief oscillations of climate
that occur at intervals much shorter than changes in
Ocean (Chapter 14). These fluctuations can rarely be
Earth’s orbital configurations?
dated accurately enough to permit firm correlations