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Lesson 7
Key Idea 1: Introduction to Feedbacks

This sample flow diagram represents both positive and negative feedbacks in a dynamic system. In all of the feedback diagrams in this lesson, red arrows will represent amplifying or positive influence, and blue arrows will represent restricting or negative influence.

The earth's climate system is directed by feedback loops (also known as feedback cycles). A feedback loop is a circuit-like system in which an initial disturbance acts as an input into the system. This creates a change in some other component of the system, known as an output, which then influences subsequent occurrences of the initial disturbance.

In a positive feedback loop, the output of the system serves to reinforce or amplify the initial disturbance. In this way, A produces B which creates more of A.

In a negative feedback loop, the output of the system acts to restrict the effects of the initial disturbance. In this case, A produces B which reduces the amount of A.

Keep in mind that a "positive" feedback loop is not necessarily desirable, just as a "negative" feedback loop in not necessarily undesirable. These words refer to the direction of change, not the desirability of their effects.