Units: 3
Offered: Spring 2011
Instructor: Adam Showman, Space Sciences 430, 621-4021
showman@lpl.arizona.edu
Course description (for catalog):
Physical and chemical processes governing the
climate of planets. Climate feedbacks and stability; greenhouse
effect, ice-albedo feedback, cloud feedbacks.
Effect of atmospheric circulation on climate. Milankovitch cycles
and ice ages. Long-term atmospheric evolution; runaway greenhouse,
Snowball Earth, atmospheric loss/collapse, faint young Sun problem.
Interaction of climate with geology/biology. Observable
signatures. Habitable zones.
Application to Earth, Mars, Venus, Titan, and habitability of
extrasolar planets.
Course objectives: This is a graduate-level course that
will provide an overview of the physics and dynamics of
the climate of planets. The target audience is graduate
students in ATMO and PtyS. Students from astronomy and
HWR may also be interested. In addition to students
primarily focusing on atmospheric studies, I hope to
attract students whose research involves (for example)
Mars/Titan geomorphology or exoplanets.
My intention is to provide a course that complements Ptys 517
("Atmospheres and Remote Sensing") as well as existing courses
in the ATMO department.
Text: Pierrehumbert's upcoming book Principles of Planetary
Climate, which will be published in June 2010, will make a good
textbook. I will also hand out detailed lecture notes and assign
reading of important papers from the peer-reviewed
literature.
Topics Covered:
Basics of radiative transfer as needed for studying climate:
greenhouse effect etc.
Feedbacks: thermal feedback, ice-albedo feedback, "condensable
gas" feedbacks (water vapor on Earth, carbon dioxide on early Mars/Venus),
runaway greenhouse, cloud feedbacks, interaction with geology/biology.
Simple (globally-averaged) models of these feedbacks. Multiple
equilibria (e.g., a warm Earth versus "Snowball Earth" states).
What controls the global-mean temperature of a planet, and its
sensitivity to perturbations over a range of timescales.
Introduction to global atmospheric circulation: What are the basic
processes that shape the circulation, determine the equator-to-pole
(or for sychronously rotating exoplanets, day-night) temperature
contrasts, etc. Theoretically possible regimes for an atmospheric
circulation; overview of circulation regimes of actual planets.
Effect of dynamics on climate feedbacks; interaction of the
circulation with climate (e.g., effect of latitudinal heat transport
on susceptibility of an atmosphere to ice-albedo feedback or
atmospheric collapse). Role of a hydrological (or for Titan, methanological)
cycle and clouds in climate.
Longer-term climate dynamics: Mechanisms for multi-annual to multi-kyr
climate dynamics. Milankovitch cycles (Earth, Mars) and the processes
that determine the ice ages (Earth) and distribution of observed glaciers
(Mars).
Climate evolution over planetary timescales: Faint-young Sun problem;
carbonate/silicate cycles; divergent evolution of Earth, Mars, Venus;
discussion of Snowball Earth; mechanisms for atmospheric loss and
the resulting climate evolution (e.g., loss of water from Venus,
loss of carbon dioxide from Mars, etc); atmospheric evolution, lakes/seas,
and the origin of methane on Titan.
Application of climate theory beyond the Solar System: What determines
the width of the "habitable zones" around main-sequence stars.
Degree to which habitable zone might depend on atmospheric mass,
composition, planetary rotation rate, gravity, or other factors.
Implications for our search for habitable worlds in the Cosmos.
Observational signatures: While this class is mostly about
fundamentals, it is important to relate theoretical knowledge
to observations. We will therefore briefly survey the relevant
observational records for Earth, Mars, Venus, and Titan,
including geology, surface morphology, geochemistry/isotopic
signatures, and atmospheric observations, to understand
how climate can be inferred. We will also discuss the
challenging issue of how observations may illuminate the
climate and habitability of exoplanets, including the topic
of atmospheric biomarkers that might signal the presence
of life on remote worlds.
Prerequisite: The course is intended for introductory
planetary science, astronomy, and atmospheric science
graduate students. Basic vector calculus and
differential equations will be used, and basic familiarity with
physics will be needed (some of this will be developed as we
go along). There are no specific course prerequisites.
Format: Course will be split between traditional
lecture format and a less formal seminar style, led
in many cases by students, where we discuss
key journal articles or topics.
Grades: The grades will be on an A, B, C, D, E scale and
will be based on two components:
40% Homework and 60% Term Project
Given the grades for the homeworks and term paper,
the assignment of the final grade will be based on a curve.
The term project is an important
aspect of this course -- my aim is to get your creative
juices flowing and get you excited
about being at the cutting edge of this field.
The term project will require a short written paper as well
as a presentation at the end of the semester (perhaps during
the final exam slot).
There are no exams in this course. However, we may
use the final exam slot
for presentations, so please reserve it in your schedules
for this course.
Course policies:
Feedback: Please let me know how you think the course is
going. Suggestions for improvements and ideas for things to try
(e.g., topics or activities you'd like to see) are both welcome.
Auditors: I would like to encourage those students auditing
this class to choose and carry out a term project. This is a good
way of cementing the course material and could lead to research
projects that we can continue after the class is over.
Late work: If an assignment is due,
you are responsible for turning it in, even if you are absent.
All assignments are due at the beginning of class on the due date.
Any assignments turned in after that time will be considered late.
I will try to be understanding, but I reserve the right to enforce
the following policy: Late assignments turned in within
one week of the due date will receive one-half credit, after which
they will receive zero credit. Please talk to me if you think you
can't finish an assignment on time.
Special needs: Students with disabilities who require reasonable
accommodations to fully participate in course activities
or meet course requirements must register with the Disability
Resource Center. If you qualify for services through DRC,
bring your letter of accommodations to me as soon as possible.
Academic Integrity: It is strongly recommended that all students
read the University of Arizona's Code of Academic Integrity.
All students in this course are expected to abide by this code,
which will be strictly enforced. Cheating will not be tolerated in
any form. Submission of any written work
that partially or fully duplicates material from the web, your
fellow students, or any other source constitutes plagiarism.
Students are encouraged to work together on the homework sets,
but unique written responses must be handed in by each student.
Instances of plagiarism will lead to a zero on that assignment, with
harsher penalties for repeat offenses or extreme cases. Plagiarism
on the term project will lead to a failing grade for the course.