what does it mean that carbon dioxide is a greenhouse gas?
A greenhouse gas is a gas in an atmosphere that absorbs and emits radiant energy within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. The primary greenhouse gases in Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone. Without greenhouse gases, the average temperature of Earth's surface would be about â18 Â°C, rather than the present average of 15 Â°C. In the Solar System, the atmospheres of Venus, Mars and ...