Does Burning Fossil Fuels Increase The Amount Of Carbon?

The burning of fossil fuels like coal, oil and natural gas is a major contributor to increased levels of carbon dioxide (CO2) in the atmosphere. This increase in atmospheric CO2 is the main cause of global warming and climate change. When fossil fuels are burned, carbon that has been stored underground for millions of years is released into the atmosphere. This leads to a disruption of the natural carbon cycle, where levels of CO2 are rising faster than the Earth’s natural sinks can absorb them. This article will examine how the chemistry of fossil fuel combustion leads to increased atmospheric carbon, the role of the carbon cycle, and the implications for Earth’s climate.

What are fossil fuels?

Fossil fuels refer to energy sources that formed underground from the remains of dead plants and animals over millions of years. The three main types of fossil fuels are coal, oil, and natural gas.

Coal was formed from ancient plant matter that decayed and was compressed underground into solid rock. It is considered the dirtiest burning fossil fuel due to its high carbon and sulfur content.

Oil, also known as petroleum, is a liquid fuel made up of hydrocarbons that originates from ancient marine organisms like algae and zooplankton. Crude oil is found in underground reservoirs and drilled to the surface.

Natural gas is a mixture of gaseous hydrocarbons, primarily methane, which formed from buried organic material. It is often found with crude oil deposits and extracted through drilling.

How fossil fuels formed

Fossil fuels like coal, oil, and natural gas are derived from the buried remains of ancient plants and animals. Hundreds of millions of years ago, the seas, lakes, and swamp forests were filled with microscopic algae, plant life, and early forms of animals. As these organisms died, they sank to the bottom of the waters and were buried by sediment and sand.

Over extremely long periods of time, heat and pressure from the depths of the Earth transformed the organic matter into coal, oil, and natural gas. Coal originated from the remains of trees, ferns, algae, and other plant material. Oil and natural gas were created from the remnants of algae, phytoplankton, zooplankton, and other marine organisms. The organic compounds underwent chemical changes, accumulating as extensive deposits of hydrocarbons locked within rock layers.

These fossil fuel deposits are concentrated in certain areas due to the specific conditions needed for their formation. The transformation of organic material into fossil fuels takes place over millions and millions of years. As a result, fossil fuel reserves are finite and nonrenewable on human timescales. The processes that created them occurred long before the appearance of modern humans.

Carbon cycle

Carbon naturally cycles between the atmosphere, land, and oceans. Plants absorb carbon dioxide from the atmosphere through photosynthesis and incorporate the carbon into their tissues. Animals consume plants, and some of the carbon becomes part of their tissues. When plants and animals die and decompose, some of the carbon returns to the soil, some is released into the atmosphere as carbon dioxide, and some enters the oceans.

The oceans contain large amounts of dissolved carbon dioxide and organic carbon. Carbon is exchanged between the ocean and the atmosphere at the surface. Ocean life also transports carbon into the deep ocean. Over very long time periods, carbon is moved into rocks and fossil fuel deposits.

This natural cycling of carbon through the atmosphere, land, life, and oceans maintains carbon dioxide levels in the atmosphere. The carbon cycle has kept the Earth’s climate relatively stable for millions of years.

Combustion releases carbon

When fossil fuels like coal, oil, and natural gas are burned, a chemical reaction takes place between the carbon in the fuel and oxygen in the air. This process, called combustion, converts the carbon atoms into carbon dioxide (CO2), a major greenhouse gas.

For example, when a lump of coal is burned, here is the chemical reaction:

C (coal) + O2 (oxygen) → CO2 (carbon dioxide)

This reaction releases energy, which is why fossil fuels are burned in the first place. But it also releases carbon atoms that were trapped underground into the atmosphere. The same process occurs when gasoline is burned in a car engine or when natural gas is burned to heat a building.

Therefore, the act of burning fossil fuels takes carbon that was sequestered underground and converts it into CO2 that is emitted into the air. This increases the total amount of carbon cycling between the atmosphere, land, and oceans.

Increased CO2 Levels

The amount of carbon dioxide in the atmosphere has risen dramatically in recent decades, according to direct measurements. CO2 concentrations are now higher than any point in at least the past 800,000 years based on data from ice cores.

CO2 levels have risen from around 280 parts per million (ppm) in pre-industrial times to over 400 ppm today, an increase of over 40%. This rapid rise started in the mid-18th century with the beginning of the Industrial Revolution as industrial activities and widespread fossil fuel burning caused sharp increases in carbon dioxide emissions.

Direct observations from modern measurement stations around the world confirm this steep rise in atmospheric carbon dioxide. For example, the Mauna Loa observatory in Hawaii has registered increases in CO2 concentration from 316 ppm in 1959 to over 415 ppm today. Other global monitoring sites show similar trends of rising CO2 over time.

The increase in CO2 levels measured across the globe matches what would be expected from the amount of fossil fuels being burned. This provides clear evidence that human activities, especially fossil fuel combustion, are the dominant cause of rising atmospheric carbon dioxide concentrations.

Human carbon emissions

When fossil fuels like coal, oil, and natural gas are burned, the carbon that had been stored underground in these deposits for millions of years is released back into the atmosphere as carbon dioxide. According to data from the Global Carbon Project, human activities have added around 2,400 billion metric tons of carbon dioxide emissions to the atmosphere since the Industrial Revolution began in the mid-1700s.

The amount of carbon dioxide released from burning fossil fuels has increased dramatically in the last century. In 2020 alone, 36 billion metric tons of CO2 were emitted globally from the combustion of coal, oil, and gas – which accounted for about 89% of total anthropogenic CO2 emissions that year. The remaining 11% came from land use changes like deforestation.

Fossil fuel emissions continue rising each year. The International Energy Agency reported that global energy-related CO2 emissions grew by 6% in 2021 as economies rebounded from the COVID-19 pandemic. This underscores how deeply the world still relies on fossil fuels for energy and that reducing emissions remains an immense challenge.

Carbon sinks

While the burning of fossil fuels releases large quantities of carbon into the atmosphere as carbon dioxide, not all of this man-made carbon stays there. Significant amounts of carbon are absorbed from the atmosphere by natural sinks like oceans and land ecosystems.

The world’s oceans are a major carbon sink, absorbing roughly 30% of human-caused carbon emissions. As CO2 dissolves into the ocean, chemical reactions take place that store carbon in seawater for varying lengths of time. Phytoplankton, which are microscopic marine plants, also take up CO2 through photosynthesis.

Land ecosystems like forests, plants, and soil absorb about 30% of man-made carbon emissions from the atmosphere. Trees and other plants utilize CO2 during photosynthesis, converting the carbon into biomass like trunks, branches, roots, and leaves. Carbon is stored in soils through the decomposition of organic matter and plant roots.

While natural carbon sinks are crucial in slowing the buildup of CO2, there are limits to how much carbon the oceans and land can absorb. Excessive emissions from burning fuels can overwhelm these storage capacities over time.

Remaining in atmosphere

Of the carbon dioxide released from burning fossil fuels, only about half is absorbed by natural carbon sinks like oceans and forests. The other half remains in the atmosphere, where CO2 persists for hundreds or thousands of years before natural processes can remove it. Unlike forests or the ocean which can only absorb CO2 at a limited rate, the atmosphere accumulates all the excess CO2 emitted from human activities.

So while natural sinks help absorb some of our CO2 emissions, a significant portion still builds up in the air. This leads to rising atmospheric CO2 levels over time as more fossil fuels are burned. While the oceans and biosphere absorb CO2, their capacity to keep up with human-caused emissions is being exceeded, leaving an increasing fraction of emitted CO2 airborne. This net increase of CO2 trapped in the atmosphere is responsible for the enhanced greenhouse effect and rising global temperatures.


As was explored in this article, burning fossil fuels like coal, oil and natural gas releases carbon that has been locked away underground for millions of years. This ancient carbon adds to the active carbon cycle, increasing the overall amount of carbon dioxide in the atmosphere and oceans. Even though carbon sinks like forests and soils absorb some of this extra CO2, a significant portion still lingers, contributing to the greenhouse effect. Therefore, the scientific consensus is clear that the combustion of fossil fuels results in a net increase in atmospheric carbon. The implications of this process on Earth’s climate underline the importance of transitioning society to cleaner, renewable energy sources that do not unleash long-buried carbon. While fossil fuels powered the Industrial Revolution and enabled the modern world, their continued use puts the planet on an unsustainable trajectory. By curbing emissions and shifting to green technologies, we can work in harmony with the carbon cycle rather than pumping excessive quantities from underground reserves. This will allow ecosystems and the climate system to maintain balance, just as they have for millennia before human industrialization.

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