Since the 1970’s Nutritionists and Doctors have been warning about the dangers of fat.  Butter was deemed to be a particularly insidious danger and its usage was discouraged.  Now the same Nutritionists and Doctors are changing their tune and saying that maybe fat isn’t such a problem and it is okay to eat butter again.  NY Times Story

Photo credit CloneHenge.com

Since the 1970’s Environmentalists and Scientist have also been warning about Global Warming (later Climate Change).  Fossil fuel were deemed to be a particularly egregious problem and their usage was discouraged.  Please refer to the butter story above for the probable conclusion of this paragraph.

Because of the chaotic nature of multi-variable problems it is really difficult to predict future outcomes.  If we have been getting it wrong about nutrition what makes you think we are getting it right about something even more complicated, like the environment?