Since 1957 the National Oceanic and Atmospheric Administration has been monitoring the air in four locations; by far the cleanest air is at the South Pole, Antarctica. Researchers are most interested in levels of carbon dioxide, the substance implicated in theories of global warming. As carbon dioxide emissions increase in the industrialized world, the same increase registers at the South Pole, but not until years later. Also tracked are ozone-depleting chemicals, methane, nitrous oxide, bromine, methylchloroform, and solar radiation. All data collected are used to predict changes in climate.
The ice and snow in Antarctica, the fifth largest continent, make up more than 90 percent of the world's fresh-water, and it is the purest in the world. Scientists who spend short periods of time there use snow melters to convert the ice to water for their personal use.
