David S Battisti
ATM S 589
Evidence for past changes in land and sea surface temperature, in precipitation and atmospheric dynamics, and in ocean circulation: both long and interannual timescales. Paleoclimate modeling and theory. Time series analysis and climate noise. Rapid climate change. Statistical reconstruction of interannual variability. Offered: jointly with ESS 589/OCEAN 589.
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 relative stability of the climate of the past 10,000 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. [The state of affairs is such that one can seriously entertain two mutually exclusive theories: the ice-age cycles are fundamentally about interactions between atmosphere/ocean dynamics and the carbon cycle (with the ice being incidental), and the ice-age cycles are fundamentally about land ice (with carbon dioxide and atmosphere/ocean dynamics being incidental).]
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 Holocene. The Holocene starts about 10,000 years ago, at the end of the last ice age, when the amount of terrestrial ice is about the same as that today. It is widely believed that the climate during the Holocene is less variable in comparison to the climate during the ice-age climate. We will examine the proxy data and modeling evidence that challenges that paradigm. In particular, it appears the climate in the tropical regions during the early Holocene (5-10k yr BP) was much different than that during the late Holocene (5ky BP to present). Finally, we will examine the efficacy of the widely held assumption that the leading patterns of year-to-year climate variability observed in the instrumental record are useful in identifying and understanding the climate variability on interannual to centennial time scales throughout the Holocene.
Student learning goals
General method of instruction
Lectures and discussion of papers.
Class assignments and grading
An important feature of the class is discussion sessions, each one focusing on a key topic. These discussions will center on the results from key papers. Two or three students will be responsible for leading each focus discussion session, though everyone is expected to contribute to the discussion. The discussion leaders will also be responsible for additional papers that resolve issues raised in the key papers, and summarize the current issues/challenges in this area of research. At least 24 hours prior to the prior to each discussion section, all students who are not assigned to lead that discussion will submit to the discussion leaders and the instructors three questions that stem from reading the key papers. The leaders should address the most important questions during the discussion session.
In addition to the student-led discussion session, there will be several mandatory problem sets. There are no exams in this course.