What is meant by a positive feedback loop, and could you give an example?

Feedback loops/systems/cycles can be either positive or negative, and it is important to understand the difference between the two. Crucially, in this case, 'positive' does not refer to something which is 'good', and vice versa. Rather, negative feedback loops counteract an initial change to a system, producing a stabilising effect, whereas positive feedback loops amplify an initial change to a system, producing a destabilising effect.One good example relates to permafrost thaw. Specifically, an increase in air temperatures causes the temperature of permafrost to rise. As a result, the active layer (the seasonally thawed layer above the permafrost) thickens while the permafrost itself simultaneously thaws. This increases the rate of microorganism activity in the soil, which causes organic material to be decomposed more quickly, and so carbon is released from the soil. Often, this is in the form of carbon dioxide or methane (particularly in wetter environments). The emission of these greenhouse gases causes temperatures to rise again, and so the cycle continues.