Earth’s climate is regulated by numerous processes that take place in different parts of the atmosphere. Take some time to review the Earth's Atmosphere learning tool from Lesson 1. Before you move on, answer the following questions:

• What gaseous substances are present in the atmosphere?
• How are these substances distributed through the atmosphere?
• What are the layers of the atmosphere?
• What determines the boundaries of the layers of the atmosphere?
• Does it get colder or warmer as altitude increases?