So fossil fuels. Everyone knows ’em. We’re very aware that burning these ancient dead things is emitting CO2 into the atmosphere. I suppose I will explain, for those curious, exactly how we know that fossil fuels are the culprit. What I thought was interesting was how small the manufacturing contribution was and how large the entry/heating contribution was! Transportation was really about where I figured it would be. But really guys I thought the other two would be flipped. Though it makes sense when you think about it. Homes are getting bigger, and it takes a lot of energy to heat and cool such large buildings. Not to mention, like, OFFICE BUILDINGS? Duh, Kale. I guess I never thought about it like that. So now when someone yells at you for not turning the light off when you leave the room, you have no reason to argue with them. And even though transportation is a small part of the fossil fuels little section of CO2 stuff, it does contribute to a sizable chunk of warming. So carpool! Ride a bike! Walk! Take the train!
Now let’s talk about ~proof~. I really won’t lie to you guys, I had a test on this literally today but I’m still a little fuzzy on the exact mechanics of this process, so please let me know if I mix something up. Also this is freaking confusing, so I’m going to try and over explain, for clarity.
Okay. Let’s talk isotopes. A generic carbon atom has 6 protons and 6 neutrons in its nucleus. An element is differentiated from another element by the number of protons in its nucleus, so a carbon atom will always have 6 protons. An isotope is a form of the same element, like carbon, but with a different number of neutrons. And a certain element can have many different isotopes, some being stable and more abundant, and other can be radioactive. For our purposes, we’re going to look at three carbon isotopes; 12C, 13C, and 14C.
| 12C | 13C | 14C | |
| condition | stable | stable | radioactive |
| protons | 6 | 6 | 6 |
| neutrons | 6 | 7 | 8 |
| abundance | 98.9% | 1.07% | trace amounts |
The cool thing about isotopes is that we can look at these characteristics and get a sense of where these carbons are in the atmosphere and where they should be.
Okay so first: researchers have collected many data over the last almost 100 years on the carbon dioxide in the atmosphere. The general trend that they have noticed is a decrease in both 13C and 14C in the atmosphere. Why is this? They used experiments, I’m going to use logic. Boink.
13C is not readily abundant just, around. So most plants use 12C for the majority of their photosynthetic activity. As a result, plants are made up mostly of 12C, AND plants regularly remove 12C from the atmosphere through their photosynthetic processes. Following? Sweet.
When plants (and animals) die, they decompose. Sometimes, they get stuck in anoxic conditions and are subjected to immense heat and pressure over thousands of years and become the fossil fuels that we use today. Instead of those fossil fuels returning to the earth ~naturally~, we have been digging them up and burning them. By burning those fossil fuels, we are returning that 12C that was in those long-dead plants to the atmosphere. And by doing THAT, we are adding more 12C to the atmosphere than 13C, thereby DECREASING the ratio of 13C:12C over a very long period of time. In conclusion, burning fossil fuels = adding CO2 to the atmosphere = global warming. Proved.
You don’t buy it yet? Don’t worry I have another example. Now let’s talk about this radioactive 14C isotope. Radioactive isotopes, specifically this carbon isotope, are super fun and have a TON of useful applications over a bunch of different practices. Why? I shall explain…
When we use 14C, we are looking at what is called it’s half-life. An isotope’s half-life is the time for 1/2 of the isotope’s mass to decay. This is useful for observational purposes over thousands to millions of years. So for example, 14C’s half-life is 5,700 years. That means after 5,700 years, 1/2 of the given 14C will have decayed. After another 5,700 years, 1/4 of the given 14C will have decayed. And so on and so forth for a long long time.
Something to note about 14C, is that it is found in very low amounts in materials over 60 thousand years old due to this radioactive decay that happens. So when we find that there is a decrease in 14C in the atmosphere, it suggests (supported by actual studies by actual scientists) that there has been a lot of recent burning of very old materials, i.e. fossil fuels.
These two examples are strongly correlated and strongly point toward fossil fuels as being a huge source for CO2 emissions into the atmosphere.
Thank you, America.
Kale Eats Plants! 