There are various different gases in the atmosphere, including 78% nitrogen, 21% oxygen, 0.93% argon, and 0.04% carbon dioxide (CO2) [1]. Now hold on, just 0.04% CO2? Yes! That’s enough to have a big warming effect on the planet [4]. How does this work?

Sunlight (also called solar radiation [5]) comes in different frequencies [6]. Around half of the light coming from the sun comes in frequencies we can see (e.g. green) and the other half in ones we can’t see (e.g. infrared and ultraviolet) [5,6]. There are three things that can happen to it once inside the atmosphere [5]:

1) About 30% is reflected back into space by clouds, gases, particles, and the Earth’s surface

2) About 20% is absorbed by the atmosphere

3) About 50% is absorbed by the land and ocean

Now comes the most important bit: when light from the sun hits the Earth, the Earth reflects it back with a changed frequency, most often infrared [5]. This is where greenhouse gases, such as CO2, come in: they absorb infrared light more than other types of light (e.g. many of those coming from the sun).

Why does this cause warming? Absorbing light, makes greenhouse gases vibrate more [10]; they are “energized” and collide with other molecules, transferring energy to them [10]. This is what heat is [11]. Therefore greenhouse gases increase the temperature of the air [10]. You can think of this as “trapping” heat close to the Earth [5].


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