Oxygen makes up about 21 %, nitrogen about 78% of the atmosphere. The last percentage consists of a whole range of trace gases such as argon and carbon dioxide. How can such a small amount, less then one % of the whole atmosphere, have such an impact on the climate? Beware people, I have some CO2 chemistry for you today!
CO2 structure. Picture from Wikipedia
CO2 is good at absorbing energy in the infrared and near infrared spectrum. It then releases some of that energy back down to earth, while some of it goes out in space again. All substances in the atmosphere behaves like this, but the problem is that it shouldn’t be so much absorption in the infrared part of the light spectra. That part should be more or less a hole. A hole which we are plugging with more and more CO2, methane, NOx and so on.
Well, that’s the very simplified version of the science anyway. But it is more difficult showing how this happens. Or how something so small can have so big impact. On my department at the university the professors explained it by using small balls with springs. Imagine the molecule on the right. The black one is carbon (C) and the red ones are oxygen (O). The sticks are electrons, two from each O connected to two from the C. This is called a double bond, which is quite inflexible and stable. If you build a model of this molecule with springs instead of sticks you will see that those springs can actually move a bit. And they do in the real molecule as well. The more energy you put in the more it moves, and the more energy it absorb for more movement the more it emit back in different frequencies later. Or something like that.
For those of you still that are awake, here comes the good part. As CO2 can absorb energy in a part of the spectrum where there used to be a lot less absorption, more will lead to energy, and in the end heat, being trapped here on earth instead of being directly reflected from the surface and out to space. Even a trace amount of this gas have such an impact. Well now we know that. Sweet! Now how do we show it so you can understand it without having studied at least high school chemistry?
Well, look at this; climateplace.org
and this Uppsalainitiativet.
The first link goes to a youtube video where a man is using ink to show how small amounts of a substance can block energy (in this case visual light). I recommend you to take a look at the video, it is rather neat. The second one is basically the same, but in a laboratory using CO2, a glass tube, an IR camera and a candle and showing how the CO2 in the tube absorbs the light. Both are excellent examples of how you can visualize CO2′s effects on the planet.
If one want to use another example of trace amounts effect on something, alcohol is an excellent example. When you have reached the legal alcohol level in the blood for driving it is actually just some ppm of ethanol in the blood stream. (DO NOT drive when you have been drinking by the way. It is dangerous for you as well for others) Arsenic is another good example, it can do a lot of damage at low levels too if it gets in the drinking water.
Right now CO2 levels are approximately 390 ppm. Compared to Oxygen or nitrogen that is a very small amount, but with a huge impact. We don’t need it to reach over 500 ppm. Or even higher then that. Every small change we do to cut back on the emissions is one step in the right direction. Visualizing and finding ways to simplify the complex science is a very important step as well. Don’t buy the “but there is so little of it” argument. It doesn’t work. As shown here.