In my last post, I wrote about how 97% of scientists around the world think that climate change is currently happening and that we are causing these changes. In that post, I shared some of the truckloads of evidence that scientists have gathered that show that climate change is happening now. But climate change has occurred many times in Earth’s past, long before humans were around and at times when the animals that seemed like they were running the planet, like dinosaurs or megalodon sharks, did not have anything to do with causing climate change. So why do scientists think the dominant animal currently on out planet, people, are causing climate change?
It is not because too many of us are forgetting to turn off our kitchen stoves. It’s mainly because of what we are doing with carbon dioxide.
Carbon dioxide is a gas in our atmosphere that traps heat. It acts like a blanket around the Earth and is the main thing keeping living things cozy and warm and from freezing to death (if you want to know how carbon dioxide traps heat, read this post I wrote).
For carbon dioxide to be able to keep everything on Earth warm, you may think the atmosphere must be full of it, but you would be wrong. Only 0.04% of the atmosphere is made of carbon dioxide, which means 99.96% of the atmosphere is not carbon dioxide. Most of the atmosphere is nitrogen (about 78%), then oxygen (about 21%), then argon (about 0.9%), and then carbon dioxide (0.04%) (and then a bunch of other gases in even smaller amounts than carbon dioxide).
Scientists measure the amount of carbon dioxide in the atmosphere in “parts per million.” As I write this at the beginning of September 2017, there are 406.69 carbon dioxide parts per million in Earth’s atmosphere. What 406.69 parts per million means is for every million pounds of stuff in our atmosphere, about four hundred of those pounds will be carbon dioxide (406.69 pounds to be precise), and over 999,500 pounds of it will not be carbon dioxide (999,593.31 pounds to also be precise).
Let’s say the dancing Elaine is a carbon dioxide molecule and the other people around her are the other types of gases in the dance party that is the atmosphere. “406.56 parts per million of carbon dioxide” means for every dancing carbon dioxide Elaine in the atmosphere there will be about 2,500 other gas people, mostly nitrogen and oxygen gas people, standing around watching her.
There are many more than one carbon dioxide Elaine in the atmosphere. There are gazillions of them around Earth, but each dancing carbon dioxide Elaine is surrounded by about 2,500 oxygen and nitrogen wallflowers. So compared to the rest of the gas molecules in the atmosphere, there are hardly any carbon dioxide molecules. But, those relatively rare dancing carbon dioxide Elaines are the main things holding onto the sun’s heat and keeping us warm.
So, you do not need that much carbon dioxide to warm the Earth. And there is the problem. Humans have been adding a lot of extra carbon dioxide to the atmosphere over the last 200 years or so.
Scientists can measure how much carbon dioxide is in the atmosphere, not just now, but also from thousands of years ago. They can do this because gas molecules from the atmosphere get caught every year in things like glacier ice and the shells of ocean organisms. By studying layer after layer of glacier ice and seafloor fossils, scientists have been able to figure out how much carbon dioxide has been in the atmosphere for over the past 400,000 years or so. When they graph the amount of carbon dioxide over that length of time, this is what it looks like:
The amount of carbon dioxide goes up and down periodically during this time period (it’s down when Earth had past ice ages), but it stays under a certain line. That is until just recently when it goes crazy and gets much higher than it has been in at least 500,000 years.
This big change happens during the Nineteenth Century. In 1850, the carbon dioxide level was about 285 parts per million, but it has been rising ever since and now it’s over 406 parts per million (and still rising).
What happened in the 1800s that caused carbon dioxide levels to rise so rapidly? Humans figured out they could get rich by burning prehistoric plant and animal remains to run machines.
The rise in carbon dioxide happened at the same time as the beginning of the Industrial Revolution. The Industrial Revolution is what we call the period in history when businessmen and inventors figured out they could make products cheaper and faster with machines than they could by hand. This was exciting because the faster and cheaper they made stuff they could sell, the more money they could make.
These machines needed a source of energy in order to be able to run. The cheapest and easiest ways to get a lot of energy back around 1800 was to burn coal, a black rock found buried in the ground that is different from most other rocks because you can set it on fire.
The new factories built during the Industrial Revolution created a huge demand for coal, which led to more people digging it up to ship it to the factories.
Once the Industrial Revolution kicked into gear it created a desire for more new technologies to allow factories to make products even cheaper and faster, as well as new technologies that could be turned into products that people would want to buy. This led to many of the inventions that make our lives more comfortable, convenient, and secure to this day, like light bulbs, telephones, and cars.
All of these new machines also needed energy to run. This increased the demand for coal, but also got people looking for other cheap forms of energy, such as oil (“oil” meaning the black liquid buried in the ground that is also called "petroleum," not the oil carnival vendors deep fry Oreos in). Petroleum oil can be turned into fuels like gasoline and kerosene that can be burned to provide energy to machines like car engines. This new source of fuel kicked the Industrial Revolution into even higher gear and more and more machines kept running by burning fossil fuels.
Burning all these fuels to power the Industrial Revolution has increased the well being of human beings as a species. One indication of that is there are a lot more people now than there were at the beginning of the Industrial Revolution. In 1800 there were estimated to be around 1 billion people alive on Earth. Today in September of 2017, there are estimated to be over 7.4 billion people alive, and a big reason for that huge jump in human population size is because the Industrial Revolution allowed more people to meet their habitat needs for food, water, and shelter, as well as to get much better health care than they were able to back when things like leeches were considered advanced medical technology.
The Industrial Revolution has had some big costs, though. Some people benefited a lot from it while other peoples’ lives may have become worse. What may turn out to be the biggest cost of the Industrial Revolution, though, is it put a lot more carbon dioxide into the atmosphere.
As I mentioned earlier, many of the machines that drove the Industrial Revolution were running on either coal, oil products like gasoline and kerosene, or natural gas (which is also found in the ground, but is different from gasoline). These sources of energy are called “fossil fuels.” Fossil fuels are literally fuels from fossils. Every time your mom pours gas into the Toyota, she is basically pouring dead prehistoric plankton juice into the car. Let me explain.
Fossil fuels were formed millions of years ago from the remains of living things. Though "fossil" probably makes you think of dinosaurs and, admittedly, it sounds way cooler to think of your mom’s Toyota running on T. Rex remains, fossil fuels pretty much all come from dead plankton in the ocean or dead plants on land.
Fossil fuels formed in places where decomposers weren’t able to eat the dead plankton and dead plants that were piling up. Over hundreds of thousands of years, pressure and heat changed these piles of dead stuff into oil (if it was plankton) or coal and natural gas (if it was plants). The fossil fuels then remained buried underground for millions of years.
Because oil and coal come from plants and plankton, they are full of carbon, which (as you may have already guessed) is one of the key ingredients in carbon dioxide.
If you have ever watched a science fiction show from the 1960’s, then you may have heard a guy with pointy ears use the phrase “carbon-based lifeforms.” All Earthlings, from microbes to cactus to your Aunt Stephanie, are carbon-based lifeforms, meaning all living things on Earth contain a lot of carbon. The carbon in your body makes up about 18% of your weight.
We get most of the carbon in our bodies from plants. Plants (and the types of plankton that act like plants, like algae) get their carbon by pulling carbon dioxide out of their environment. They use the carbon dioxide to make sugars through a process called photosynthesis. The sugars then store carbon and energy.
If plants and plankton die and nothing eats them, the carbon stays in their remains. If the dead plants and plankton over time turn into oil or coal, their carbon goes into the oil and coal too. If we then dig the fossil fuels up and burn them, we release the carbon that has been trapped in the oil and coal for millions of years. Once the carbon is free, it combines with oxygen to make carbon dioxide, which then goes into the atmosphere. When you see smoke coming out of a coal-fueled factory or exhaust coming out of the tailpipe of the car, a lot of the stuff rising in the air is escaping carbon dioxide.
This adds extra carbon dioxide to what is already cycling in and out of the atmosphere.
Scientists can measure how much carbon dioxide we have been releasing over time. From 1757, just before the Industrial Revolution, to 2014, humans have released about 1.5 trillion tons of carbon dioxide into the atmosphere (1,480,000,000,000 tons to be a little more precise). If all that carbon dioxide stood on your bathroom scale, it would weigh almost three quadrillion pounds (2,960,000,000,000,000 pounds to also be more precise), about the same weight as roughly 42 trillion ten-year old kids. That’s a lot of extra carbon dioxide that has been added to the atmosphere.
That creates a problem because, since carbon dioxide is like a blanket, as we keep adding extra carbon dioxide to the atmosphere, we are basically putting more blankets around the Earth. The more blankets we put around the Earth, the warmer it gets.
As I wrote in my last post, scientists have observed that the Earth has been getting warmer over the last 150 years or so. This graph shows the change in average global temperatures and the change in the amount of carbon dioxide in the atmosphere. Notice they move in pretty much the same direction as one would expect since carbon dioxide traps heat.
You might be wondering, “How can people have produced 1.5 trillion tons of carbon dioxide, particularly since I have never personally started a coal fire?” Even if you don’t burn fossil fuels in your house, you are still burning fossil fuels, just not in your house (though if your furnace or kitchen stove run on natural gas, like my furnace does, then you are burning fossil fuels in your house).
- Every electronic device in your house is running on electricity. Though the electricity may come from renewable or nuclear energy sources, most likely it comes from natural gas or coal. In 2016, over 64% of electricity used in the United States came from fossil fuels (33.8% of it from natural gas and the other 30.4% of it from coal).
- You are also using electricity when you go to school, work, a store, a restaurant, an arcade, or pretty much any other building, since the lights, screens, air-conditioners, heaters, etc. all run on energy that you are at least partially using. Even outdoor public spaces have electronic devices like street lights and traffic signals that are there for everyone's use.
- Every time you ride in a car, bus, or plane, you are burning petroleum fuels like gasoline.
- Every product in your home, including the materials that make-up your home, required energy to manufacture and get shipped from the factory to you. Most of that energy came from fossil fuels.
- All the food you eat also required energy to grow, harvest, keep cold, ship to you, and cook.
So we are each burning a lot of fossil fuels to live, even if most of those fossil fuels aren't burning where we can see them.
Just to give you some actual numbers, according to the World Bank, in 2013 (the latest I could find data) on average, each person on Earth released 5.0 metric tons of carbon dioxide that year, which is about 11,000 pounds of carbon dioxide per person. If that same average amount per person happens this year, then that means about 7.5 billion people are each going to add around 11,000 pounds of carbon dioxide to the atmosphere in 2017 (82,500,000,000 pounds total).
And that's the world average. Some countries produce a lot more carbon dioxide than others, like, for instance, the United States, where I live. In 2013, we released 16.4 metric tons (36,156 pounds) of carbon dioxide per person. That's more than three times the world average.
So that’s why scientists think people are causing climate change. They know carbon dioxide makes the atmosphere warmer. They know people are burning a lot of fossil fuels. They know burning fossil fuels adds a lot of carbon dioxide to the atmosphere. They know the amount of carbon dioxide in the atmosphere is rising. And they know the Earth keeps getting warmer as the carbon dioxide levels keep rising.
So that’s what scientists think. What do I think about their findings about climate change? I will tell you in my next blog post.
PS. There are other ways scientists have determined we cause climate change, like removing forests, and by releasing methane, which is another powerful greenhouse gas, but because I only have so much time, you’ll have to look up how they contribute to climate change yourself. Sorry!
Online References and Resources:
The Atlantic. "The Hockey Stick: The Most Controversial Chart in Science, Explained."
EOS. "Current Carbon Emissions Unprecedented in 66 Million Years."
NASA. "The Human Factor: Understanding the Sources of Rising Carbon Dioxide."
NOAA. "Carbon dioxide levels rose at record pace for 2nd straight year."
Popular Science. "How we know that climate change is happening—and that humans are causing it."
Popular Science. "Six irrefutable pieces of evidence that prove climate change is real."
Scientific American. "Atmospheric Carbon Dioxide Hits Record Levels."
Scientific American. "The Crazy Scale of Human Carbon Emission."
Scientific American. "If carbon dioxide makes up only a minute portion of the atmosphere, how can global warming be traced to it? And how can such a tiny amount of change produce such large effects?"
University of Michigan Center for Sustainable Systems. "Carbon Footprint Factsheet."
Photos and Images:
Click the photos and images used above to find their sources (except the first photo, which was taken by my dad about thirty years ago).