I'm thinking that if they were to put in Health in a future expansion it would be global health on a per city basis.
Pluses would be: Aquaduct, Hospital, Medical Lab, and forest.
Minus would be: population, marsh, jungle, flood plains, factories, and nuclear fall out.
In addition, the University would remove the negative of nearby jungle tiles, and the Dutch UB would remove the negative of nearby marshes.
Effects would be:
Zero or Positive health: No affect other than being added to the GA counter [just like global happiness]
Health between -1 & -9: 10% less population growth per point; and this negative number being added to the GA counter.
Health between -10 & -19: ZPG. 50% chance of a random tile within your civ getting struck by global warming per turn.
Health -20 or worse: One random tile within your civ gets struck by global warming per turn.
Health can be implemented like global happiness. But it won't be ******** like global happiness.
This is how is should work: every city generates "health +" and "health -" points. Those points form global health for that Civ. But there will be another stat - world health. It will be a sum of global health numbers from every Civ. Nuclear fallout will generate a penalty for global health. If world health will be good - every Civ will receive improved production, hapiness,growth, etc. When it's bad - every Civ will be punished and global warming will turn grasslands and plains into deserts.