The Greenhouse Effect

greenhouse effect     climate past    climate present    climate future

The key to understanding climate change is the greenhouse effect.  The greenhouse effect is a process by which the atmosphere traps heat and keeps the surface of the earth warmer that it would otherwise be.  The effect is natural, and the problem is not that it exists, but that we are increasing its effect.

Energy from the sun in the form of light passes through the atmosphere and is either absorbed by the surface or reflected back into space. If the surface is white (such as snow), much light will be reflected. If the surface is darker, more light will be absorbed, and the surface will heat more.

The surface then radiates this heat into the sky in the form of infrared radiation. You can feel infrared radiation when you are in front of a wood fire or a stove that is on. Some molecules in the atmosphere, which are greenhouse gasses, absorb this radiation and reflect it back to the earth.  Although these gases make up only a small percentage of the atmosphere, they have a huge effect. Currently, the average temperature of the earth’s surface is 60 degrees F (15 degrees C).  Without the greenhouse effect, the earth would be almost uninhabitable; all infrared radiation would escape into space and the surface temperature would average 0 degrees F (-18 degrees C).

The most important of these gases is carbon dioxide, which we add to the atmosphere every time we burn fossil fuels or forests.  As such, we are increasing the effect of the greenhouse effect, and the average temperature of the planet is getting warmer. Since the beginning of industrial times (about 1850), carbon dioxide in the atmosphere has increased by one third, thus increasing the greenhouse effect and global temperatures.