Negative Feedback Loop
Recall DaisyWorld, the fictional planet covered with a population of white daisies and black daisies. As the planet warms, the higher temperature leads to the growth of more white daisies. An increase in white surface from the flowers reflects more energy, which leads to a decrease in the planet’s temperature. Although quite simplified, the cooling effect caused by the increased population of white daisies in this model is an example of negative, or balancing, feedback. In a negative (balancing) feedback loop, the initial change to the system is decreased, or diminished, by the resulting feedback loop.
In the DaisyWorld model, the star shining on DaisyWorld gets brighter over time. The graph shows what the temperature of the planet would be like if there were no daisies (orange line) and if there were white daisies and black daisies (pink line). In a world with daisies, the ratio of black daisies and white daisies reaches a balance over time that maintains a comfortable growing temperature for both populations.
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A simple example of negative feedback on Earth is the fact that a warmer planet gives off more heat, in the form of infrared radiation, to space. Therefore, if Earth’s temperature increases (for example, due to increased heating by the Sun or increasing atmospheric carbon dioxide concentration), the planet will radiate more heat to space, which helps to balance that change.
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Review It
What would happen to the temperature of DaisyWorld if its sun continued to get brighter and there were no daisies on the planet?
a. The temperature would keep increasing.
b. The temperature would keep decreasing.
c. The temperature would eventually stabilize.
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