Feedback Loops: Interactions that Influence Arctic Climate

In the climate system a "feedback loop" refers to a pattern of interacting processes where a change in one variable, through interaction with other variables in the system, either reinforces the original process (positive feedback) or suppresses the process (negative feedback). In order to model and predict arctic (and global) climate variability correctly, feedback loops must be understood. Two major feedback processes that scientists consider in studies of arctic and global climate change are described below in simple terms. In nature, the processes are considerably more complicated.

Temperature—Albedo Feedback

Rising temperatures increase melting of snow and sea ice, reducing surface reflectance, thereby increasing solar absorption, which raises temperatures, and so on. The feedback loop can also work in reverse. For instance, if climate cools, less snow and ice melts in summer, raising the albedo and causing further cooling as more solar radiation is reflected rather than absorbed. The temperature—albedo feedback is positive because the initial temperature change is amplified.

Temperature—Cloud Cover—Radiation Feedbacks

Feedbacks between temperature, cloud cover and radiation are potentially important agents of climate change. However, they are not well understood and research in this area is active.

It is thought that if climate warms, evaporation will also increase, in turn increasing cloud cover. Because clouds have high albedo, more cloud cover will increase the earth's albedo and reduce the amount of solar radiation absorbed at the surface. Clouds should therefore inhibit further rises in temperature. This temperature—cloud cover—radiation feedback is negative as the initial temperature change is dampened.

However, cloud cover also acts as a blanket to inhibit loss of longwave radiation from the earth's atmosphere. By this process, an increase in temperature leading to an increase in cloud cover could lead to a further increase in temperature - a positive feedback.

Knowing which process dominates is a complex issue. Cloud type plays a strong role, as do cloud water content and particle size. Another factor is whether the cloud albedo is higher or lower than that of the surface. Research indicates that the effect of this feedback in the Arctic may be different than in other latitudes. Except in summer, arctic clouds seem to have a warming effect. This is because the blanket effect of clouds tends to dominate over reductions in shortwave radiation to the surface caused by the high cloud albedo.