Global warming has a variety of causes.  One of the largest factors contributing to global warming is the general problem of overpopulation and its many effects.

The greater number of people consume more items which take more energy to make, they drive more cars, and create larger amounts of garbage.  These factors all increase the global warming problem.

Many different gases can increase the planet's temperature.  The number of different products and human activities that contribute to global warming are so numerous that finding solutions to the problem is very difficult.

Using a refrigerator releases dangerous gases, turning on the lights requires energy from a power plant, and driving to work causes gas emissions from the car.  Countless other normal activities lead to global warming.

Though having an atmosphere is important, the greenhouse effect may be making it excessively thick.  The levels of gases covering the Earth have soared with industrialization, and developed countries now produce about 75% of greenhouse gases.

The most common gas is carbon dioxide, accounting for about 50% of all greenhouse gases.  Other gases, including methane, CFCs, nitrogen oxides, and ozone, also contribute to forming the greenhouse layer.

Because these gases are produced by so many important and common processes, limiting their production to prevent global warming will be difficult.  As population increases and Third World countries begin to use greater amounts of energy, the problem may expand rather than contract.