Answer:
Albedo is a feedback mechanism that can either be positive or negative, depending on the context.
Albedo is defined as the fraction of solar radiation that is reflected by a surface, such as the Earth's surface or a cloud. When the albedo of the Earth increases, it means that more solar radiation is being reflected back into space, which can lead to a cooling effect on the planet. This is known as a negative feedback, as it acts to counteract the original warming trend.
On the other hand, if the albedo decreases, meaning that more solar radiation is absorbed by the Earth's surface and atmosphere, it can lead to warming. This is known as a positive feedback, as it acts to reinforce the original warming trend.
For example, melting snow and ice in the Arctic can lead to a decrease in albedo, as the darker ocean or land surface that is revealed absorbs more solar radiation than the highly reflective snow and ice. This causes further warming, which leads to more melting, and so on. This is an example of a positive feedback loop that can amplify the effects of global warming.
In summary, albedo can act as either a positive or negative feedback mechanism, depending on whether it is increasing or decreasing.