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Course
Description
In this
course we will provide an introduction to the broad field of
“Paleoclimatology” by focusing on the examination of three important
and unsolved problems: the toggling between glacial and interglacial
conditions over the past two million years; the remarkably abrupt,
possibly global scale climate changes seen throughout the last glacial
period; the decadal to centennial scale variability in the past 1000 years.
We will first examine the ice-age problem. The ice-age cycles are
clearly paced by changes in insolation that occur because of changes in
the properties of the Earth’s orbit around the Sun: this is the
so-called Milankovitch theory. There is a close relationship between
insolation, ice volume and carbon dioxide. The processes that link
these variables are still uncertain. Hence, it is not surprising that
several theories for the ice ages exist, some of which are not
complimentary. We will examine the climate proxy data, the theories and
the modeling to determine what is known and what is uncertain about the
ice-age cycles, and to illuminate the key questions that are being
asked by investigators working on this problem today. This include
the mechanisms liking changes in carbon dioxide to changes in ice volume and insolation, and role of carbon dioxide changes in the glacial cycles, and the extraordinary rate of termination of the major glaciations.
The second problem we will examine is the causes for the remarkable
abrupt climate changes seen during the last ice age, that have not been
since: the so-called Dansgaard-Oescgher events and the Heinrich events
(iceberg discharges) that may be associated with them. We will
summarize and critiqued the observations that define theses events and
the current ideas of the processes responsible for them.
In the final section of the course, we will turn to the climate of the last 1000 years, which is mainly deduced from a plethora of proxy records throughout the globe but particularly in the northern hemisphere. Some of the reconstructions show that the natural variability on decade to centennial time scales is sufficiently small that the warming trends seen in the 20th Century can only be due to human factors. Other reconstrcutions show sufficiently large variability that one can not attribute the 20th Century trends to human forcing, and that there is nothing special about the recent warmth in the instrumental records. Front and center in this debate are the differences in the various tools that are used to develop each reconstruction, and how that impact the answer. We will examine these issues and explore tools that are being developed to better constrain the reconstruction based on physics and thermodynamics, rather than by arbitrary mathematical choices in mapping the proxy records to climate variables.
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Evaluation
There will be about seven problem sets in this course. Some of the assignments will allow us to quantitatively examine some of the more important issues that we will explore during the course. Other assignments will illuminate
the benefits and drawbacks of some key analaysis tools that are frequently used (and misused) in paleoclimate studies, such as spectral analaysis and reduced state-space methods of reconstructing climate using multiply proxies.
There are no exams in this course.
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Required
Readings
See Syllabus
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