Bias easy to explain (Score 1)

Environmentalists are biased for a very simple reason, common to all human beings: self-interest. Levels of government funding and charitable donations are directly related to the perceived threat posed. Environmentalists, whether working in academia or Greenpeace, obtain more money, and increase their job security, by overstating the threat. Another, non-financial gain is the increased respect and appreciation society affords individuals working in this field, which is also proportionate to the perceived danger.

This happens without overt personal malice necessarily involved, since individual environmentalists may feel it is justified (as well as their jobs and status) in order to avert a catastrophy they really believe lies in the future. However, the effect is still malicious, since the data does not support the increased funding and higher social status.