5.2.1 Carbon Dioxide

5.2.1 Carbon Dioxide

Carbon Dioxide (CO2)

Fossil fuels—coal, oil, and natural gas—are rich in carbon (C) and hydrogen (H). When we burn them for energy, carbon combines with oxygen from the air to form carbon dioxide (CO2). In fact, CO2 is the largest chemical product by mass released from fossil fuel combustion.

 Fun connection: Yes, humans also exhale CO2 when we breathe! And plants need CO2 for photosynthesis—the process that powers life on Earth. So CO2 itself isn't "bad". The problem is scale and speed:

  • Natural carbon cycle: Plants absorb ~120 billion tons of CO2/year; oceans and soils absorb more.
  • Human addition: Burning fossil fuels adds ~38 billion tons of extra CO2 per year (as of 2024)—far more than natural systems can absorb quickly.

Use the “our world in data” interactive below to see which countries emit the most carbon emissions total.

Check for Understanding

Use the panel to the right of the chart to look at CO2 emissions for other countries and regions and consider the following questions. 

The US was the largest total carbon emitter until about 2005. Which country emits more carbon today? 

    Answer: China

What trend do you see with carbon emissions in Europe?

What about Asia? 

What can you infer about the differences between Europe and Asia?  Why do you think there is such a stark difference between carbon emissions in these two areas of the world?

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