The earth absorbs some of the energy as heat, and reflects some of it back into space. That trapped heat, so the theory goes, makes the Earth even warmer, a process that scientists call the greenhouse effect. The earth has become about one degree Fahrenheit warmer this century. Some climate experts predict that the planet could become up to six degrees warmer in the next century. That could cause coastal flooding, disrupted agricultural patterns, and damage to the health of wildlife, animal life, and humans unaccustomed to the new conditions.
Some skeptics dispute the scientific data and calculations underlying the entire theory.
Others don't dispute the earth is growing slightly warmer but say that isn't necessarily a dangerous trend. The scientific battle has spilled over into the policymaking arena. At the earth summit in Rio de Janeiro in 1992, the U.S. and more than 150 other countries agreed to voluntarily cut back their greenhouse gas emissions to 1990 levels by the year 2000. But in fact, the opposite trend has developed in many countries. Just this week, the Energy Department reported that in 1996, U.S. emissions of greenhouse gases increased by 3.4 percent.