According to the EPA, global surface temperatures have increased between 0.6 and 1.2 degrees Fahrenheit in the last hundred years, and the 20th century's 10 warmest years have occurred since 1984. Rising temperatures are melting glaciers and raising ocean levels. The chief cause of the rising temperatures, most scientists agree, is carbon dioxide in the atmosphere resulting from industrial and civilian use of fossil fuels. Environmental activists say it's possible to shift to cleaner energy sources, but oil companies and some manufacturers are trying to convince people otherwise. The clearing of forests, especially those in the tropics, is another major concern of environmentalists.
Rainforests shelter many plant and animal species.
Many political and business leaders are hoping that advancing knowledge and new technology will solve the problems like the ones described in this story. Most activists we spoke with doubt it, however. Indeed, they fear that rapid technological innovation is actually widening the gap between rich and poor. As of 1999, the US, with less than 5 percent of earth's population, had more computers than the rest of the world combined. Justice activists are skeptical of other advancing fields, as well, particularly genetic engineering and nanotechnology, which alter substances at the molecular and atomic levels, respectively.