The greenhouse effect is the rise in temperature that the Earth experiences because certain gases in the atmosphere (water vapor, carbon dioxide , nitrous oxide , and methane , for example) trap energy from the sun. Without these gases, heat would escape back into space and Earth's average temperature would be about 60 ºF colder. Because of how they warm our world, these gases are referred to as greenhouse gases.

	Centre for science and environment
	United Nations Environment Programme