Global warming occurs when Pollution is allowed to stay on the map, beginning in the Industrial age. It can affect the world by turning Plains into Deserts. Global warming can be avoided by building Mass Transit, Recycling Centers, and more environmentally friendly power plants. If there is a mass nuclear exchange, the resulting pollution will speed up Global warming incredibly, turning the world into a desert.
There are four stages, each stage taking several turns.
- When any pollution is on the map, a red ball appears next to the science light bulb.
- The ball turns pink/orange color.
- The ball becomes yellow.
- The ball changes to white.
If there is still pollution on the map at the end of the fourth stage, some Plains squares will become Desert, or some coastal squares will turn into Swamp. The stages are then reset, and the cycle begins again.