What is our atmosphere and what’s in it?
We previously covered off what the greenhouse effect is, how greenhouse gases affect the climate, and how humans have caused a massive increase in the amount of greenhouse gases in the Earth’s atmosphere. Now before we look at the sources of those greenhouses gases, let’s take a moment to understand what our atmosphere is and the make up of it.
So what is our atmosphere? According to NASA, it is “similar to a jacket for our planet. It surrounds our planet, keeps us warm, gives us oxygen to breathe, and it is where our weather happens.” Basically, the atmosphere makes Earth habitable. That’s not to say Earth is unique in having an atmosphere, it’s just how ours is formed makes it possible for life to exist. By contrast, Venus has such a thick atmosphere that temperatures on the surface average 475 degrees Celsius and Mars’ atmosphere contains no ozone layer, meaning harmful radiation from the Sun is able to reach the surface of the planet, although scientists think that Mars once had an atmosphere similar to Earth’s.
As the following video from the UK’s Met Office explains, Earth’s atmosphere is divided into a number of layers, from the troposphere (closest to the Earth’s surface) through to the exosphere (which eventually leads to interplanetary space):
As to explaining what makes up our atmosphere, again NASA does a much better job than I ever could:
“By volume, the dry air in Earth’s atmosphere is about 78.08 percent nitrogen, 20.95 percent oxygen, and 0.93 percent argon.
A brew of trace gases accounts for the other approximately 0.04 percent, including the greenhouse gases carbon dioxide, methane, nitrous oxide and ozone. Yet while these greenhouse gases make up just a tiny percentage of our atmosphere, they play major roles in trapping Earth’s radiant heat and keeping it from escaping into space, thereby warming our planet and contributing to Earth’s greenhouse effect.
The largest greenhouse gas by volume is actually the one most people tend to overlook: water vapor, whose concentration varies significantly depending on temperature. As the temperature of the atmosphere increases, the amount of humidity in the atmosphere also goes up, further heating our planet in a vicious cycle.
Tiny solid or liquid particles known as aerosols, which are produced both naturally and by human activities, are also present in variable amounts, along with human-produced industrial pollutants and natural and human-produced sulfur compounds.”