Feedback loops in the climate system
One of the challenges in understanding how climate change works and for scientists who model climate change is identifying and collecting data on feedback loops. A feedback loop involves a coupled system that collectively acts to accelerate or decelerate an initial change. There are two kind of feedback loops: negative and positive.
Consider a ball placed on the following three topographic features. If gently placed as shown, the ball will remain in place. However, lets consider what happens to the ball when someone comes by a gives it a gentle tap. Compare what might happen for the "stable" and "unstable" feature.For the "stable" case, gravity it going to try to return the ball back to its original location, whereas the "unstable" case, gravity will act to accelerate the movement of the ball away from its original location.
Feedback Loops
A negative feedback loop (e.g., the "stable" example) has an outcome that inhibits or limits the process from continuing to happen. A simple example is the negative feedback loop associated with your morning cup of coffee cooling off. Initially, your coffee is very hot relative the air around it, so it has a rapid cooling rate. But as the heat energy from your coffee transfers to the air and the temperature difference between the coffee and the air diminishes, the rate of cooling actually slows. It eventually stops when your coffee reaches the air temperature; it can't get any cooler than the air around it because there is no longer a differential across which to transfer heat.
A positive feedback loop (e.g., the "unstable" example), on the other hand, has an outcome that amplifies or multiplies the process occurring. One of the simplest examples of a positive feedback loop is an interest bearing saving account. As you put money into your savings account, you accrue interest, thereby increasing the net monies in your account. The more money in your account, the more interest you make, and so on. This hypothetical would incentivise saving money to make money. Of course, this assumes inflation is non-existant.
Earth systems are full of feedback loops, many of which are associated with the climate system. One of the most commonly discussed feedback loops in the context of climate change is called the ice-albedo feedback. As you learned earlier in this module, surfaces like snow and ice have the highest albedo of naturally-occuring land cover surfaces, and reflect most incoming solar radiation that reaches them. As global temperatures warm and the extent of icy, white surfaces decreases due to melting, a positive feedback ensues where more insolation is absorbed, the ice melts faster, and more area is now less reflective.
A positive feedback loop (e.g., the "unstable" example), on the other hand, has an outcome that amplifies or multiplies the process occurring. One of the simplest examples of a positive feedback loop is an interest bearing saving account. As you put money into your savings account, you accrue interest, thereby increasing the net monies in your account. The more money in your account, the more interest you make, and so on. This hypothetical would incentivise saving money to make money. Of course, this assumes inflation is non-existant.
Earth systems are full of feedback loops, many of which are associated with the climate system. One of the most commonly discussed feedback loops in the context of climate change is called the ice-albedo feedback. As you learned earlier in this module, surfaces like snow and ice have the highest albedo of naturally-occuring land cover surfaces, and reflect most incoming solar radiation that reaches them. As global temperatures warm and the extent of icy, white surfaces decreases due to melting, a positive feedback ensues where more insolation is absorbed, the ice melts faster, and more area is now less reflective.