The earth is so big, it can be hard to imagine how sensitive our climate is to the greenhouse gas emissions we produce. The ground under our feet seems to extend out forever, as does the sky over our head. It can be difficult to intuitively grasp how impactful humans can be on our environment when the earth and our atmosphere seems so endless. Yet really sound scientific inquiry has shown us that we are that impactful, and frequently to ill effect. There is no issue where this is more true than our changing climate.
A Climate Change Thought Experiment
So in an effort to demonstrate just how sensitive the earth’s climate is to relatively small changes in our atmosphere, I wanted to lead you through a thought experiment. Imagine if we shrunk our planet down to a more manageable size - that of a football field.
To be more precise, imagine that the earth’s diameter, instead of being 7,926 miles at the equator, was exactly 100 yards. You could start at one goal line, say the city of Quito, Ecuador, and start walking through the earth’s crust. At the midfield, you’re in the very center of the planet’s core, and when you reach the other goal line, you pop back out at Singapore. Get the idea?
Climate Change and the Atmosphere
Now, to be clear, I’m just talking about our planet’s landmass. We also have an atmosphere, that seemingly endless sky I mentioned above, which extends out into the endzones of the football field. You might think that it extends quite a ways into the endzone, maybe a few yards at least, but you would think wrong. At this scale, the earth’s atmosphere (measured out to a demarcation point called the “Kármán line”) would only stick out 0.784 yards into each endzone, which is about two feet and four inches.
So essentially, all of the air on our planet fits within that less-than-a-yard band of atmosphere when you think of the earth at this scale. Shockingly thin, isn’t it?
Earth's Atmosphere and Climate Change
When it comes to climate though, most of the earth’s air has no impact at all. Due to their molecular structure, gasses like nitrogen, oxygen, and argon do not trap any of the sun’s energy and keep it held against the planet’s surface (the so-called greenhouse effect). Heat energy passes right through them, unlike greenhouse gases like carbon dioxide, methane, and nitrous oxide.
So what if we unmixed the gasses in our dry atmosphere (in other words, excluding the water vapor that is constantly moving through the water cycle) and took them out?
Well, nitrogen is about 78% of the dry atmosphere, so there goes 1.83 feet of what was sticking out into the endzones. Oxygen is another roughly 21%, taking up another 0.49 feet. Argon is only about 0.93% of the atmosphere, so it takes up 0.26 inches. But if you’re following along, that’s more than 99% of all of our atmosphere.
Carbon Dioxide: The Greenhouse Gas Effect Culprit
Every bit of the greenhouse effect is caused by the remaining 0.07% of our atmosphere. If we didn’t have it, the earth would be about as hospitable to life as the moon is.
On our football field, that corresponds to 0.02 inches, or about half of a millimeter. It’s tiny! Of that amount, carbon dioxide makes up the clear majority. As of the end of March 2022, carbon dioxide makes up 0.0420% of the dry atmosphere (in other words, 420 ppm, or parts per million). That’s about 0.3 millimeters on our football field.
I want to say it again, so you get the main point in all of this math that I’ve thrown at you. If the earth were the width of a football field, then the gases that keep our planet warm enough to live on would be less than half a millimeter wide!
The Sensitivity of the Planet's Thermostat
Tracking Greenhouse Gas Emissions in Georgia