The Carbon Cycle Explained: The Delicate Balance of Carbon in the Atmosphere

Science & Tech
May 4, 2021
Avely Pütsep

It’s easy to have mixed feelings about carbon. Is it good or bad?

On one hand, it’s the foundation of life on Earth. At the same time, it’s entwined with climate change. It’s the most commonly produced greenhouse gas and traps heat in the atmosphere.

To understand climate change, we need to understand carbon cycles.

Welcome to Carbon Cycle 101:

  • What is the basis of the carbon cycle?
  • Wait, what’s the carbon cycle and why is it important?
  • How does the carbon cycle work and what affects it?
  • Why are carbon reservoirs important?

What is the role of carbon in the atmosphere?

To understand carbon cycles, you first need to know why carbon matters and where it comes from. The answer lies in the role of carbon in the atmosphere.

Why is carbon important?

Without carbon, life as we know it wouldn’t exist.

Carbon is the central element in organic compounds. These compounds make up everything from cells to structures of organisms and carry out life processes, which makes them necessary for life.

Carbon regulates the Earth’s temperature, forms DNA molecules, and provides energy. Pretty awesome, right?

Where does carbon dioxide come from?

The answer to how does carbon get into the atmosphere is human activity and natural sources.

Examples of human actions releasing carbon into the atmosphere are:

  • CO2 emissions from fossil fuels
  • land-use change
  • extensive deforestation

Examples of natural sources of CO2:

  • volcanoes erupting
  • organisms dying
  • wildfires blazing
Examples of human actions releasing carbon into the atmosphere include land use change and fossil fuels

What is the carbon cycle?

The carbon cycle is nature’s way of recycling carbon atoms. Carbon atoms continually and repeatedly travel from the atmosphere to Earth and back into the atmosphere.

Essentially, the carbon cycle is a non-stop circulation of carbon.

So, the carbon cycle definition is a series of processes where carbon circulates through the land, ocean, and atmosphere.  

❗️ Note: Because Earth is a closed system, the amount of carbon never changes. The amount of carbon in a reservoir does change as it’s either moving to another reservoir or in another reservoir already.

Why is the carbon cycle important?

If it wasn’t for the carbon cycle, most carbon would be in the atmosphere or stored entirely in rocks. The carbon cycle keeps carbon moving. ♻️

And it’s good that it does as the carbon cycle is vital to life on Earth!

The carbon cycle keeps carbon levels balanced and this balance keeps Earth hospitable for life.

How does the carbon cycle work?

The carbon cycle is everywhere and no living organism is left out. Even most objects are included! Carbon is in your computer, the coffee you drink, and the candles you burn.

How does carbon get from the atmosphere to plants?

n the atmosphere, carbon is attached to oxygen in a gas called CO2. Through photosynthesis, the plant pulls CO2 from the air to make “food” for itself for plant growth.

How does carbon get from plants to animals?

When an animal eats a plant, the carbon from the plant moves to the animal. Animals that eat other animals get carbon from their food, too.

How does carbon get from plants to the soil?

When a plant or animal dies, their decaying bodies bring carbon into the soil. Some of the carbon gets buried and turns into fossil fuels in millions of years.

How does carbon get from living things to the atmosphere?

‍Believe it or not: every time you exhale, you release CO2 into the atmosphere! Also, once a living thing dies, be it a plant or a human, carbon is released into the atmosphere.

How does carbon get from fossil fuels to the atmosphere?

Easy answer: carbon gets to the atmosphere from fossil fuels when fuels are burned.

Fossil fuels are burned to power things like factories and vehicles.  During this, carbon quickly enters the atmosphere.

How does carbon get from the atmosphere to oceans?

Oceans and other bodies of water absorb carbon from the atmosphere, where carbon dissolves into the water. So the role of water in the carbon cycle is an important one.

What activities affect the carbon cycle?

The carbon cycle is affected by nature and human activities.

And, surprise-surprise, human actions are having a greater impact than ever. Cutting down trees, making more factories, driving more gas-powered cars: these all contribute to the way carbon moves around the Earth. These changes add more greenhouse gases to the atmosphere, causing faster climate change.

If it wasn’t for human interference, the carbon in fossil fuels would leak slowly into the atmosphere. By burning natural gas, oil, and coal, we accelerate the “leaking”. The carbon that took millions of years to accumulate is now released yearly in vast amounts.

The carbon cycle balances out the exchange of carbon between reservoirs. That is until humans intervene. The natural cycle adds and removes CO2, keeping a balance. Humans however add extra CO2 without removing most of it.

The extra carbon needs to go somewhere. There are big reservoirs: oceans, rocks, and a lot of carbon enters the atmosphere. More on carbon reservoirs in the next chapter.

What percentage of CO2 in the atmosphere is man-made?

It’s not known exactly what percentage of CO2 in the atmosphere is man-made.

What is known is that carbon levels are dangerously high: they’re the highest they’ve been in the last 800 000 years!

What is known is that carbon levels are dangerously high as they’re the highest they’ve been in the last 800 000 years

Why are carbon reservoirs important?

Changes to the carbon cycle affect each carbon reservoir in a specific way.

Wait, what is a carbon reservoir? A carbon reservoir is where carbon is stored. This includes anything from plants and animals to rocks and the atmosphere.

The main carbon reservoirs are trees, oceans, rocks, and the atmosphere. But really the list is very very long.

The land is full of versatile carbon reservoirs

Carbon reservoirs on land include plants, soil, forests, rocks, and animals.

About 80% of carbon is locked in rocks: as inorganic carbon in the Earth’s crust and mantle or lithosphere.

The amount of carbon that plants absorb changes from year to year, but the amount of CO2 they can take in has increased since the 60s.

Talking of trees, the MVPs of carbon absorption on land: the older the tree, the greater its potential to offset and store carbon, slowing climate change.

How much carbon does a tree sequester? Well, it can take decades for a tree to start absorbing and sequestering carbon. So biomass is an integral part of Earth’s carbon cycle.

Biomass materials like plants and forests need to be sustainably farmed. That’s what Single.Earth stands for.

The ocean is the biggest carbon reservoir

What is the largest reservoir of carbon? 🌊🌊 The ocean is the biggest carbon reservoir, by far.

Oceans have 10x more capacity than freshwater and therefore absorb more carbon.

Oceans absorb substantial amounts of CO2 so they’re a big help in consuming a lot of the greenhouse gases from human activities. However, it’s still not known for sure how badly it affects marine life and the biosphere.

The more CO2 in the oceans, the more acidic the water becomes and the higher the danger.

Just one example: ocean acidification affects marine life by putting shell-building animals in danger. When the ocean becomes more acidic there’s less bicarbonate. Yet, this bicarbonate is what shell-building animals like corals need. Their shells end up thinner and more fragile as a result.

Why is the level of carbon in the atmosphere so important?

It’s easy to think carbon in the atmosphere is bad. In actuality, CO2 in the atmosphere is very important as it controls the Earth’s temperature.

Without greenhouse gases, the temperature on Earth would be a freezing -15°C or 5°F.

With too many greenhouse gases, temperatures could be around 420 degrees Celsius or 788 Fahrenheit.

It is crucial to save the forests and wetlands we still have left to keep healthy ecosystems intact.

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