The Critical Zone

Lesson Overview


To properly understand the varying effects of climate on the Critical Zone, we must understand Earth's atmosphere and the range of phenomena that occurs within it. In this lesson, we will explore the basic structure of the atmosphere, the carbon cycle, basic atmospheric chemistry, atmospheric carbon dioxide, and greenhouse gases, radiative forcing, physical climate processes and feedbacks, and regional climate issues. We will briefly consider the links between the atmosphere and the Critical Zone throughout the lesson.

As you read through the assigned material, you should always make note of and consider the potential link between the subject matter and the Critical Zone. For example, what effect does atmospheric chemistry have on the Critical Zone and how are they linked? We will return to considering these links in more detail later in this lesson and in Lesson 12.

Much of our understanding of the atmosphere and climate system derives from the recent focus on the impact of human society on the greenhouse gas content of the atmosphere and global climate change. The Intergovernmental Panel on Climate Change (IPCC) (go there and read "About IPCC") is a scientific panel established by two organizations of the United Nations in 1988 to evaluate the risk of climate change from human activity. The main activity of the panel is to publish special reports based on assessments of peer-reviewed and published scientific literature—four reports have been published in three volumes each, the most recent in 2007. Much of the background information and reading for Lesson 2 was culled from the 3rd and 4th assessment reports.

Did you know . . . ?

In 2007, the IPCC received a Nobel Peace Prize for its work. Among the 2,000 contributors (including Al Gore), there were five Penn State faculty who shared in the prize: Michael Mann, Richard Alley, Bill Easterling, Klaus Keller, and Anne Thompson were all substantial contributors to the Intergovernmental Panel on Climate Change.

What will we learn about in Lesson 3?

  • Fundamentals of the atmosphere
  • Overview of the climate system
  • C cycle and atmospheric CO2
  • Basic atmospheric chemistry
  • Greenhouse gases
  • Radiative forcing
  • Physical climate processes and feedbacks
  • Regional climate issues

What is due for Lesson 3?

Lesson 3 will take us one week to complete. As you work your way through these online materials for Lesson 3, you will encounter additional reading assignments and hands-on exercises and activities. The chart below provides an overview of the requirements for Lesson 3. For assignment details, refer to the lesson page noted.

Please refer to the Calendar in Canvas for specific time frames and due dates.

Lesson 3 Activities
"Calculating Carbon Footprints" page 6 Post to the Lesson 3 - Carbon Footprint discussion forum, then discuss.


If you have any questions, please post them to our Questions? discussion forum (not e-mail), located under the Discussions tab in Canvas. I will check that discussion forum daily to respond. While you are there, feel free to post your own responses if you, too, are able to help out a classmate.