Greenhouse gases are the gases present in the earth's atmosphere which reduce the loss of heat into space and therefore contribute to global temperatures through the greenhouse effect. Greenhouse gases are essential to maintaining the temperature of the Earth; without them the planet would be so cold as to be uninhabitable. However, an excess of greenhouse gases can raise the temperature of a planet to lethal levels, as on Venus where the pressure of carbon dioxide contributes to a surface temperatures of about 467 °C (872 °F). Greenhouse gases are produced by many natural and industrial processes, which currently result in high levels carbon dioxide in the atmosphere. Based on ice-core samples and records current levels of carbon dioxide higher than during immediately pre-industrial times, when direct human influence was negligible.

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 (something in poo), for example) trap energy from the sun. Without these gases, heat would escape back into space and Earth’s average temperature would be about 60ºF colder. Because of how they warm our world, these gases are referred to as greenhouse gases. paw print

Greenhouse Have you ever seen a greenhouse? Most greenhouses look like a small glass house. Greenhouses are used to grow plants, especially in the winter. Greenhouses work by trapping heat from the sun. The glass panels of the greenhouse let in light but keep heat from escaping. This causes the greenhouse to heat up, much like the inside of a car parked in sunlight, and keeps the plants warm enough to live in the winter.
The Earth’s atmosphere is all around us. It is the air that we breathe. Greenhouse gases in the atmosphere behave much like the glass panes in a greenhouse. Sunlight enters the Earth's atmosphere, passing through the blanket of greenhouse gases. As it reaches the Earth's surface, land, water, and biosphere absorb the sunlight’s energy. Once absorbed, this energy is sent back into the atmosphere. Some of the energy passes back into space, but much of it remains trapped in the atmosphere by the greenhouse gases, causing our world to heat up.

The greenhouse effect is important. Without the greenhouse effect, the Earth would not be warm enough for humans to live. But if the greenhouse effect becomes stronger, it could make the Earth warmer than usual. Even a little extra warming may cause problems for humans, plants, and animals.

Short version:

1. Solar radiation passes through the clear atmosphere.
2. Most radiation is absorbed by the Earth's surface and warms it.
3. Some solar radiation is reflected by the Earth and the atmosphere.
4. Some of the infrared radiation passes through the atmosphere, and some is absorbed and re-emitted in all directions by greenhouse gas molecules. The effect of this is to warm the Earth's surface and the lower atmosphere.
5. Infrared radiation is emitted from the Earth's surface.