"Umm, what do you do if after filtering out all the cranks and nuts, you find 97% of the experts agree you have a brain disorder but the recommendations of the experts range from minor medications to removing the brain to try to save it?"

I doubt that is highly unlikely to play out like that. There would generally only be two or three major recommendations that would have large factions behind them.

I know you are trying to tie this back to climate change, but it should be noted that in that case, scientists do not make policy recommendations. They should be identifying and proving the problem (mankind's actions are putting enough greenhouse gases in the atmosphere that it is affecting the climate). Then identifying and showing the different effects of the problem. Policy makers (who are elected by the public) can then use that information to decide on a course of action. Maybe it is subsidizing energy sources that do not produce greenhouse gases, maybe it is subsidizing removal of greenhouse gases. Maybe it is penalizing the "Tragedy of the Commons" effects that carbon producers rely on to cheaply produce their product. Maybe it is just getting the public to accept the effects of higher greenhouse gases (rising seas, higher asthma rates, different weather patterns, etc.).

There will be winners and losers in either case so that is why policy makers need to make those decisions.