About climate change
Climate change, also called global warming, refers to any significant change in climate lasting for decades or longer. A certain amount of climate change can result from natural factors, such as variations in the sun's intensity or, over very long periods of time, changes in the earth's orbit or position of the continents. Scientists believe that the current climate changes are primarily a result of human activities. As a result, the earth is expected to warm substantially during just a few decades, returning it to conditions not seen for hundreds of thousands or even millions of years.
The greenhouse effect
The earth’s atmosphere acts like a pane of glass in a greenhouse, trapping the sun’s heat in the lower atmosphere and causing temperatures at the surface to warm. Life depends on this natural greenhouse effect; without it, average temperatures would be 60º F colder.
Some of the atmospheric or greenhouse gases that trap heat include water vapor, carbon dioxide (CO2), methane, nitrous oxide, ozone and certain synthetic fluorocarbons. Some of these occur naturally, but since the industrial age began, greenhouse gas concentrations have increased beyond natural levels. Studies of ice cores show that CO2 levels have risen by a third since the pre-industrial era. Most of that increase comes from burning fossil fuels, including coal and petroleum, to run our cars, factories and power plants.
About seven billion metric tons of carbon are released through human activity every year. CO2 added today remains in the atmosphere for 100 years or more, which means that CO2 released to the atmosphere each year accumulates and results in increasing levels of CO2 in the atmosphere. Since scientists say that CO2 is responsible for three-fourths of any predicted warming, temperature increases are inevitable.
The average temperature of the Earth’s surface has increased by about 1.2 to 1.4º F since 1900. Other aspects of the climate are also changing, such as precipitation patterns, snow and ice cover, and sea level.
For additional background information, refer to: