HUMAN ACTIVITIES CAN disrupt the balance of the natural system that regulates the temperature on [Page 470]Earth. This natural regulating system is known as the greenhouse effect. As human societies burn fossil fuels, and adopt it to increasingly sophisticated and mechanized lifestyles in the developed world, the amount of heat-trapping CO2 and CH4 in the atmosphere has increased. By increasing the amount of these heat-trapping gases in the atmosphere, humankind has enhanced the warming capability of the natural greenhouse effect.

Most of Earth's heat is re-radiated toward space, but some is trapped by greenhouse gases in the atmosphere. This is a natural effect that keeps Earth's temperature at a level necessary to support life.

This human influence (in addition to the natural release of these gases) on ...