- Greenhouse gases, including carbon dioxide, methane and water vapor, trap heat in the Earth's atmosphere and warm the planet.
- In general, the greenhouse effect is a good thing. Without greenhouse gases, the temperature on Earth would be too cold to support life. With too many, it would heat up beyond survivable levels. Earth is sometimes called the Goldilocks Planetbecause it is "just right."
- Since 1958, the amount of carbon dioxidein the atmosphere has been measured from an observatory on Mauna Loa, a volcano in Hawaii.
- The pre-industrial concentration of carbon dioxide in the atmosphere was 280 parts per million(ppm). As of March 2009, it has reached 387 ppm.
- Today, the amount of carbon dioxide is higher than at any time in the last 650,000 years.And the Earth's average temperature is increasing faster than ever before.
The Intergovernmental Panel on Climate Change projects that temperatures will rise 3.2 - 7.2 degrees Fahrenheit in the 21st century. Dramatically reducing levels of global warming pollution may keep the rise in the lower part of this range.