ABOUT CARBON DIOXIDE: The concentration of carbon dioxide in the atmosphere has increased by about 30 percent since the beginning of the industrial revolution in the late 1800's. Most of this increase comes from using fossil fuel -- coal, oil and natural gas -- for energy, but approximately 25 percent of the carbon came from changes in land use, such as the clearing of forests and the cultivation of soils for food production. Natural sources of atmospheric carbon include gases emitted by volcanoes, and respiration of living things. We breathe in oxygen, and breathe out carbon dioxide.
ABOUT AIR POLLUTION: Air pollution is made up of many kinds of gases, droplets and particles that can remain suspended in the air. This makes the air dirty. The easiest way to visualize airborne particles (also called aerosols) is to exhale outside on a cold day and watch the fog come out of your mouth as water vapor forms into water droplets. The same thing happens in the atmosphere, but for different reasons. Under certain conditions individual molecules come together and form particles -- a chemical soup. In the city, air pollution may be caused by cars, buses and airplanes, as well as industry and construction. Ground-level ozone is created when engine and fuel gases already released into the air interact when sunlight hits them. Ozone levels increase in cities when the air is still, the sun is bright and the temperature is warm.
The American Geophysical Union and the American Meteorological Society contributed to the information contained in the TV portion of this report. This report has also been produced thanks to a generous grant from the Camille and Henry Dreyfus Foundation, Inc.