20.7: Climate Feedback Loops

Climate Feedback Loops

Based on the number of variables and how they change over time, it is readily apparent how complex and interconnected the climate system is. For instance, when a volcano erupts, it 1) adds some thermal energy to the climate system, 2) produces aerosols that block solar radiation from hitting the Earth’s surface, and 3) produces greenhouse gases that retain heat. Notice that these factors do not influence climate in a consistent way. The change of one variable as the result of another is called feedback Links to an external site., which can be positive (reinforcing) or negative (discouraging). For climate, a feedback that increases an initial warming is called a positive feedback whereas a feedback that reduces an initial warming is a negative feedback.

Positive feedback loops Links to an external site. enhance or amplify changes, moving the system away from equilibrium. For instance, if Earth warms, ice melts and reduces albedo, which results in additional warming. This can also occur in the opposite direction: if Earth cools, ice forms and increases albedo, which results in additional cooling.

Negative feedback loops Links to an external site. dampen or buffer changes, holding a system to some equilibrium state and making it more stable. For instance, if the Earth warms, more surface area becomes arid, resulting in an increase in the amount of dust in the atmosphere, which reflects solar radiation, causing cooling. Again, the opposite works: if the Earth cools, less surface area is arid, resulting in a decrease in the amount of dust in the atmosphere, which causes warming.

Understanding the climate system requires identifying all significant climate variables, how they are related to each other, the speed at which they can change, and the magnitude and direction of change for each feedback loop. The best way to gain a better understanding of the climate system is to study it through geologic history.