The Greenhouse Effect Explained

The greenhouse effect can be thought of a little bit like the blanket you cover yourself with at night to keep warm. Our planet has an atmosphere around it containing certain gases that trap heat energy helping to keep the planet warm. And, no matter what anyone tells you, the greenhouse effect is a very good thing. No scientist would ever challenge that statement. The greenhouse effect is an entirely natural process. It was taking place long before the first lump of coal was ever burnt or the first cow let one rip.
But what exactly is it and how does it work?
The explanation starts with energy waves, presented here on the electromagnetic spectrum. Radio waves, light, x-rays… they’re all basically the same thing. We often think of them as travelling in waves and the thing that makes them different from each other is the length of that wave. To understand the greenhouse effect we’re interested in infrared waves, a fancy term for heat waves, as well as visible light. Notice that infrared waves have a longer wavelength than light waves. That’s an important detail.
As you probably know, we get our energy from the Sun. The energy from the Sun reaching our planet is mostly in the form of light energy. We’ll call this shortwave radiation to keep things simple.
Some of that energy is absorbed by the planet’s surface, causing an increase in temperature. Energy that has been absorbed and warmed an object can be then be released, but it isn’t released as light energy. The energy is released, or re-emitted, to use the correct term, as infrared waves (heat, in other words). Remember that these heat waves have a longer wavelength than the light waves that first reached the surface. From here on in we’ll call these infrared waves long wave radiation.
Next, let’s look space. Space is cold. Its baseline temperature is about -270 degrees Celsius. Very cold indeed. Far too cold for life to exist. Fortunately, since our planet orbits close to the Sun (close in astronomical terms, that is) we are kept well above that temperature.
However, if the Earth were to absorb and re-emit energy the way I’ve already described, and all of that long wave radiation is allowed to leave the Earth system, the average temperature of the surface would be around -18 degrees Celcius. That’s better than the -270 of space, but still fairly cold. We know the Earth isn’t really that cold… so what are we missing? Enter the greenhouse effect.
Fortunately for us, specific gases in our atmosphere, gases such as carbon dioxide, methane and others, all known as greenhouse gases, are able to absorb and re-emit the long wave radiation coming from the surface of the Earth. Now remember, shortwave radiation reaches us from the Sun, but long wave radiation is radiated from the surface. These greenhouse gases are not able absorb short wave radiation reaching the Earth. Consequently, they let the Sun’s energy in, but then trap some of it as it tries to leave. This trapping of heat energy obviously raises the temperature in the atmosphere, Earth’s surface and it’s oceans.
So basically, our atmosphere traps some of the heat energy in the Earth system, keeping it that bit more warm. As a result of Earth’s natural greenhouse effect the average temperature on our planet is about 15 degrees Celsius, 33 degrees warmer than it would be without any greenhouse effect.
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