Monday, October 1, 2018

What The Heck Is the Greenhouse Effect?

The greenhouse effect is “the trapping of the sun's warmth in a planet's lower atmosphere due to the greater transparency of the atmosphere to visible radiation (light) from the sun than to infrared radiation (heat) emitted from the planet's surface.”

Visible light and infrared light are both forms of electromagnetic radiation. Visible light is of a higher radiation frequency that penetrates the atmosphere and its gases with ease. It strikes the surface of the planet and there’s a step down in the energy level to the infrared radiation level which we feel as heat. This heat radiates back out towards space. However, certain gases such as CO2 absorb and re-emit the infrared energy, thus creating a blanket effect much like greenhouse glass does. Or, shall we say, the thicker the CO2, the warmer  the atmospheric blanket becomes.

Diagram of visible light warming Earth and infrared light radiating away from Earth’s surface:

Visible light:

IR infrared radiation:

Global Warming: How Is It That Atmosphere Acts As A Blanket?

The thermodynamics: a warm object in a cold environment radiates its heat away until it decreases its temperature to match the outside environment.

A blanket does two very important things to make it harder for heat to leave:
1. The blanket is going to absorb the heat your body is radiating. By heating up to some intermediate temperature and being in the way of your radiation, it inhibits the rate of heat flow from your body to the outside environment, meaning you lose heat more slowly than you would otherwise. And…
2. The blanket is partially reflective, meaning that some of the heat emitted from your body either gets reflected outright from the blanket back towards you or absorbed and re-emitted from the blanket back towards you.
And as anyone who’s ever been underneath too many blankets can tell you, this can even make you too hot very quickly!

The blanket of CO2 in the atmosphere acts as a blanket.

For the science behind how the atmosphere acts as a blanket, read the last half of...
...beginning with-
“...Our atmosphere is nearly all nitrogen and oxygen gases, which are practically transparent to both the light emitted by the Sun and the heat radiated by the Earth. But after nitrogen and oxygen, the next most common elements in our atmosphere are water vapor, carbon dioxide...