17. Global warming and climate change.
PART 1: What is climate change?
Weather changes all the time. The average pattern of weather, called climate, usually stays pretty much the same for centuries if it is left to itself. However, the earth is not being left alone. People are taking actions that can change the earth and its climate in significant ways.
Carbon dioxide is the main culprit.
The single human activity that is most likely to have a large impact on the climate is the burning of "fossil fuels" such as coal, oil and gas. These fuels contain carbon. Burning them makes carbon dioxide gas. Since the early 1800s, when people began burning large amounts of coal and oil, the amount of carbon dioxide in the earth's atmosphere has increased by nearly 30%, and average global temperature appears to have risen between 1° and 2°F.
Carbon dioxide gas traps solar heat in the atmosphere, partly in the same way as glass traps solar heat in a sunroom or a greenhouse. For this reason, carbon dioxide is sometimes called a "greenhouse gas." As more carbon dioxide is added to the atmosphere, solar heat has more trouble getting out. The result is that, if everything else stayed unchanged, the average temperature of the atmosphere would increase.
As people burn more fossil fuel for energy they add more carbon dioxide to the atmosphere. If this goes on long enough, the average temperature of the atmosphere will almost certainly rise. You can learn more about how this works, and uncertainties in scientific understanding, from Details Booklet Part 1.
If global warming occurs, not every day or every place will be warmer. But on average most places will be warmer. This will cause changes in the amount and pattern of rain and snow, in the length of growing seasons, in the frequency and severity of storms, and in sea level. Farms, forests, and plants and animals in the natural environment, will all be affected.
Other gases and dust also matter.
Carbon dioxide is not the only...