Lake Champlain Hares

Each of the following, if true, supports the zoologist's reasoning EXCEPT:

Zoologist: In the Lake Champlain area, as the North American snowshoe hare population grows, so do the populations of its predators. As predator numbers increase, the hares seek food in more heavily forested areas, which contain less food, and so the hare population declines. Predator populations thus decline, the hare population starts to increase, and the cycle begins again. Yet these facts along cannot explain why populations of snowshoe hares everywhere behave simultaneously in this cyclical way. Since the hare population cycle is well correlated with the regular cycle of sunspot activity, that activity is probably a causal factor as well.

Answer: Local weather patterns that can affect species' population changes can occur both in the presence of sunspot activity and in its absence. 

This presents an alternate cause that is independent of the sun spot behavior (local weather patterns). Alternate causes ALWAYS weaken causal arguments, so this is the correct answer in this strengthen except question.