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carbon dioxide

Take a deep breath and exhale slowly. Your body just released carbon dioxide, a colorless gas that's essential to life on Earth. Carbon dioxide is one of the greenhouse gases that absorb and hold heat in Earth's atmosphere, keeping our planet warm enough for life to exist. But humans are increasing carbon dioxide levels in the atmosphere above historic levels. As carbon dioxide levels rise, so do global temperatures.

Stats

Definition: a colorless, heat-absorbing gas that is naturally present in the atmosphere
Formula: CO² (1 carbon atom + 2 oxygen atoms)
Unit of Measure: PPM (parts per million); number of molecules in 1 million molecules of air
Sources: burning fossil fuels, plant and animal respiration, decaying organisms, weathering rocks
Cool Fact: Without greenhouse gases like carbon dioxide, Earth's surface would be frozen!

Story

Carbon Cycle
Like water moves through the water cycle,
carbon moves through the carbon cycle.

Carbon moves through the air, water, soil, and even living things. Oceans absorb carbon dioxide from the atmosphere. Plants use carbon dioxide and sunlight to make their own food. Animals and plants alike release carbon dioxide through respiration and when they decay. Marine animals use carbon dissolved in water to make their shells. Shells build up to form rocks. Rocks release carbon dioxide through weathering. Different parts of this cycle can take anywhere from hours to tens of millions of years.

This cycle has kept a healthy balance of carbon dioxide in the atmosphere--just enough to keep Earth's temperatures within a certain range and for life to exist. But now, human actions are disturbing the balance. When we burn fossil fuels, we rapidly release carbon that had been locked within Earth into the atmosphere. The carbon combines with oxygen in the air to form carbon dioxide.

Stumper

The primary way that humans release carbon dioxide into the air is by:

breathing

burning fossil fuels

eating plants

Correct!

We produce carbon dioxide when we burn fossil fuels like coal, oil, and natural gas. The more carbon dioxide there is in the atmosphere, the more heat is absorbed, and the warmer the planet gets.

Fact or Fiction

Today, the atmosphere contains more carbon dioxide than at any time in at least the past 800,000 years.

Fact

Fiction

Fact

Antarctic ice core evidence shows that the big jump in atmospheric carbon dioxide of the past century is extraordinary. It has never risen this much, this fast, in the past 800,000 years.

Fact or Fiction

The ocean holds over fifty times more carbon dioxide than the atmosphere.

Fact

Fiction

Fact

In the past 200 years, the ocean has absorbed about 30% of all carbon dioxide emissions from human activities. The increasing carbon level is threatening marine organisms like corals.

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Explore the connections between technology, population and rising atmospheric CO₂.

Take a closer look at how the atmosphere keeps our planet warm.

Correct!

Fact

Fact

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