Shaun Tanner has been a meteorologist at Weather Underground since 2004.
By: Shaun Tanner , 6:38 AM GMT on September 05, 2011
Thank you all for reading last's weeks opening blog in my ongoing educational series. For those of you just joining the class, welcome! My hope is that by the end of this series, you will all be experts in the atmosphere that you call home. Or, at the very least, you will have armed yourself with a few tools that you can use to make informed decisions on how you affect the environment.
If you missed my opening blog, please get caught up by reading it here. In it, I talk about my rationale of writing this blog series as well as give a brief introduction on what weather and climate actually are.
My goal is to write a new lesson every week. Since I have slightly more time on the weekend, these new blogs will more likely come out before the beginning of the workweek so you will have all week to read it. But, if Mother Nature intervenes (hurricane, tornadoes, stomping in puddles outside my house) then I will be late in posting the lessons. Okay, are you ready for this week's lesson? Last week we learned about weather and climate. This week we will learn about the air we all breathe.
What is in the air we breathe?
Several years ago, I was an avid watcher of "Who Wants to be a Millionaire" (oh be quiet, you know you were too). One of the questions on the show was, "What is the most abundant gas in the lower atmosphere?" The contestant stared at the four choices before him for quite some time before making the correct decision. After I got done jumping around my living room screaming the correct answer, I wondering to myself how much of the general public even knows what the answer is. I mean, isn't it important to actually know what our lungs pull in with every breath? Well, now it is your time to learn.
There are two categories of gases in the atmosphere:
These are gases that are constant in time and space. What that means is that their input is balanced by their output. So, if gas A is a permanent gas and I take one molecule of gas A out of the atmosphere, then somewhere else on Earth, one molecule of gas A was put into the atmosphere. These gases are constant...permanent.
Don't make it harder than it sounds. These are gases that are...variable. If you want to make it difficult, then these gases are such that input and output are not balanced and thus can vary in time space. If you think really hard, you can probably come up with one very important variable gas that is literally part of your life everyday. It manifests itself as liquid in the atmosphere so you can see it. Water vapor! Sure, get it? Water vapor is a variable gas, obviously, because sometimes you have clear skies and the water vapor quantity is low, and sometimes you see clouds in the sky and everything feels more humid (humidity is the measure of water vapor in the air).
So, what is the most adundant gas in the atmosphere and is it a variable or permanent gas? Again, if I asked you to name some of the gases in the atmosphere, you could probably easily come up with several. One of those should be oxygen. Right? Right?
Figure 1. Table showing both the permanent and variable gases in the atmosphere.
In the table above, the left side shows the most abundant permanent gases and the right side are the variable gases. I want to draw your attention to the top two permanent gases. Nitrogen makes up 78% of our lower atmosphere. 78%! That number is amazing everytime I see it. Why it takes up so much of our atmosphere will be explained in a minute. The second most abundant gas in the lower atmosphere is oxygen at ~21%. For you math majors, I want you to add up the Nitrogen and Oxygen percentages. 99%! So, what I am telling you is that the two most abundant gases in the atmosphere account for 99% of the gases in the lower atmosphere by volume (as opposed to weight). So the rest of the gases in the table, both permanent and variable, take up only 1% of the atmosphere. Amazing, isn't it?
Before I get into specifics, I want to again draw your attention to the left hand column of the table. Argon, Neon, Helium, Xenon. If you know anything about chemistry (I don't blame you if you don't), then you should know that those elements have something in common. They are called Noble Gases. Without getting into the nitty-gritty, the basics you should know about Noble gases is that they don't like friends. They don't like to combine with other elements to create anything remotely exotic. So, when they do get put up into the atmosphere, they stay there because they don't like to make friends and combine with the other more friendly elements up there.
Now, for some specifics. I want to run down some sources and removal processes for some of the permanent gases.
Nitrogen is put into the atmosphere by volcanoes. In fact, volcanoes put a lot of stuff into the atmosphere.
Also, when animals and plants decay (including yourself when you pass on), Nitrogen is recycled back into the atmosphere.
One of the big removal processes comes from soil bacteria. If you think about it, fertilizer is pumped full of Nitrogen because plants love it. Why do they love it? Because it is abundant in the atmosphere.
Another way Nitrogen leaves the atmosphere is by way of our friendly ocean plankton. They do a good job of eating it up.
Nitrogen is inert. What that means is that it doesn't like friends either. So, when it gets put into the atmosphere, it can stay for a long time.
Think back to your second grade class and you should be able to answer this one. Photosynthesis! When plants exhale, they put oxygen in the air. We have a lot of oxygen because we have a lot of plants!
Oxygen is a very friendly element. It combines with many other elements and when it does, the atmospheric form, 02, that makes up 21% of the atmosphere goes away. One of these chemical reactions occurs when plants and animals decay. Oxygen does a good job in breaking things down.
It is also removed during the breathing process, which is the other end of the photosynthesis reaction.
Now let's take a look at a couple of the variable gases.
The best way for water vapor to get into the air is by evaporation. Liquid water evaporates from the ocean (yes, and other bodies or water) and becomes water vapor up in the sky.
Also, volcanoes do a great job in pumping water vapor into the atmosphere.
It is removed from the atmosphere when it precipitates. It is that easy!
It is an interesting note that water is the only substance that can occur as gas, liquid, and solid in the lower atmosphere. That is quite a feat!
The last one I want to take a look at is carbon dioxide.
You! When you breathe, you exhale carbon dioxide.
Also, burning fossil fuels is a big unnatural deal. We will cover this in a much later lesson.
Another big deal is deforestation. I usually say deforestation is a double-whammy because when you cut down a tree, the tree is no longer able to take carbon dioxide out of the air. Not only that, when trees are cut down, they begin to decay. When vegetation, such as trees, decays it RELEASES carbon dioxide into the atmosphere. So, it is a double-whammy...they can no longer absorb carbon dioxide AND they release it into the atmosphere when they are dead.
I will leave you with this last figure:
Figure 2. The Keeling Curve that shows the increasing concentration of atmospheric carbon dioxide over the last several decades.
What you see is one of the most famous curves in all of atmospheric science. It is called the Keeling Curve and was named after Charles David Keeling. Beginning in 1958, Mr. Keeling took measurements of atmospheric carbon dioxide twice a year at the Mauna Loa Observatory in Hawaii. Why Hawaii? Well, if you think about it, Hawaii is in the middle of a giant bathtub called the Pacific Ocean, well away from major influences from large cities and landmasses. It was a pristine an experiment place as you can get.
There is one observation you should see right away. That is, the curve has gone up relentlessly since 1958. Granted, carbon dioxide makes up only a tiny sliver of the atmospheric gases, but as we will see in Lesson 2, it doesn't take all that much carbon dioxide to shift the balance of the atmosphere.
There is another observation which I find even more fascinating. Do you see how the curve bounces up and down over the course of a year? Think for a minute before you read on about what could cause that. What could cause carbon dioxide to decrease rapidly throughout the year, only to see it increase later that year?
The answer, of course, is plants! During the Winter months in the Northern Hemisphere (the hemisphere with the most plant life), the plants die or become dormant and are no longer able to absorb carbon dioxide out of the atmosphere. Carbon dioxide concentration goes up. In the Spring and Summer, the plants come back to life and absorb the carbon dioxide. Thus, A VARIABLE GAS! This also illustrates how important plants are to the atmosphere.
Ah, I love it when a plan comes together.
See you next week everybody. Your homework is to think about what you are breathing.
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