1. Because our atmosphere gases trap and return a major portion of the heat radiating from the Earth.
2. Global warming, as many people think, is a phenomenon that the temperature is increasing. Snowing in winter indicates the low temperature. However, snowing does not mean that it is not global warming.
3. Because water absorbs microwave radiation and therefore, weakens the signals given out by the devices.
4. In short run, air quality should be the problem. For example, if CO2 concentration increase 3 times, you won’t be able to survive in few minutes. In long run, global warming should be the problem since its effects take many years to surface.