Feedback Mechanisms of Climate Change

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  • 0:00 Feedback Mechanisms
  • 1:47 Ice-Albedo Feedback
  • 3:24 Water Vapor-Cloud Feedback
  • 4:38 Atmosphere-Ocean Interactions
  • 5:22 Atmosphere-Biota Interactions
  • 6:42 Lesson Summary
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Lesson Transcript
Instructor: Joanne Abramson

Joanne has taught middle school and high school science for more than ten years and has a master's degree in education.

Our climate is performing a constant balancing act. Discover what happens when this balance is upset, how our planet responds, and the important feedback mechanisms at play.

Feedback Mechanisms

Just like this rock formation, the earth's climate represents a delicate balancing act. There is a precise equilibrium between the energy coming in from the sun and the energy being reflected back into space from the planet's surface.

When an event occurs, such as humans adding greenhouse gases to the atmosphere, this equilibrium is disturbed. In response, the climate will either warm up or cool down to reset the balance. In this example, greenhouse gases prevent solar radiation from being reflected back into space. However, to keep the balance, energy must be reflected back into space from the planet. So, the climate warms up, allowing more energy to be released as heat, until the original balance has been restored.

The climate responds through what is referred to as feedback mechanisms. A feedback mechanism is a process that allows a system, such as climate, to self-regulate in response to a change, such as increasing greenhouse gases.

A common example of a feedback mechanism is the thermostat in your home. When the temperature inside becomes too cold, the heater switches on, warming up the air. Once the air reaches the correct temperature, the heater switches off, and the air starts to cool back down. This process repeats, allowing you to keep your room at a stable temperature.

The earth's climate has several feedback mechanisms, such as the ice-albedo feedback, the water vapor-cloud feedback, the atmosphere-ocean interactions, and the atmosphere-biota interactions.

Ice-Albedo Feedback

Albedo is derived from the Latin term for 'whiteness' and refers to how reflective a surface is. The more ice there is on the earth's poles, the higher the earth's albedo.

When the earth is very 'white,' it becomes more reflective. You have likely noticed this effect if you have ever been skiing. When the earth has a high albedo, more of the sun's radiation is reflected back into space and less is absorbed by the planet. This has the effect of keeping our planet cooler.

Here is how the ice-albedo feedback loop operates. The amount of radiation that the earth receives from the sun does not always stay the same. When the sun sends more radiation to the earth's surface, the planet starts to heat up. This increase in temperature causes the ice at the poles to melt. Less ice means that the planet's albedo decreases. Less radiation is reflected back into space and more is absorbed, causing the earth to heat up even more. A warmer planet means more ice melting, less radiation reflected back, and more absorbed, and so on. As you can see, the ice-albedo feedback loop causes the planet to continue to heat up.

This is what is referred to as positive feedback. In positive feedback, the initial effect is enhanced or increased. In this case, the initial effect was warming caused by increased solar radiation. The positive feedback loop causes the warming to continually increase.

Water Vapor-Cloud Feedback

Lucky for us, and everything else on our planet, the ice-albedo feedback loop does not continue unchecked. This is where the water vapor-cloud feedback loop, an example of negative feedback, comes into play. In negative feedback, the initial effect is counteracted or decreased. The thermostat we discussed in the introduction is another example of negative feedback.

As you have probably noticed, on a very foggy day, water droplets in the air make it hard to see. This is because they are scattering and reflecting the sun's rays. While this can make it hard to drive your car, it also helps keep the earth cool as the sun's radiation is bounced back into space.

As the planet warms up, the oceans begin to evaporate at a higher rate. This water vapor in the atmosphere leads to the formation of clouds, or water droplets in the sky. The clouds (notice that they are white like the snow) reflect the sun's radiation away from the planet, causing the earth to cool back down. Thus, the water vapor-cloud feedback loop keeps the planet from heating up forever.

Atmosphere-Ocean Interactions

Another example of positive feedback can be found in the earth's atmosphere-ocean interactions.

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