How does burning fossil fuels increase atmospheric carbon dioxide?

Burning fossil fuels—such as coal, oil, and natural gas—increases atmospheric carbon dioxide (CO₂) because these fuels are composed of organic carbon that was removed from the carbon cycle in prehistoric times.1

When these fuels are burned for energy, the carbon they contain undergoes combustion, a chemical reaction where the carbon reacts with oxygen to produce CO₂. This process releases vast amounts of carbon that had been stored in Earth’s crust for millions of years back into the atmosphere.231

Because the rate at which human activities release this carbon far exceeds the capacity of natural "sinks"—such as oceans and vegetation—to absorb it, the concentration of CO₂ in the atmosphere has risen significantly since the Industrial Revolution. This accumulation of CO₂ is a primary driver of global warming and climate change, as the gas traps infrared radiation and warms the lower atmosphere.245