The rising average global temperature is having the greatest effect on the

Arctic

Explanation:

The global temperature is on the rise, though not as much as it is often portrayed in the media. It is a slow process, but even though the changes in the temperature are seemingly small, they manage to cause changes, at some places almost unnoticeable, at some places more dramatic. The area that is most affected so far is the Arctic. The reason for this is that the Arctic is mostly covered with ice, but ice over an ocean not over land. As the temperature rises, the edges of the ice are melting, thus entering the ocean waters, and the cycle of the ocean currents. As the water circulates, it peaks up warmth in the lower latitudes, moves toward the Arctic and manages to penetrate further north and contributes to further melting of the ice. The process continues constantly, so the little by little the Arctic is changing its appearance, which unfortunately causes lot of problems for the flora and fauna adapted to it.