A brief history of carbon in our atmosphere

Carbon is essential to life on Earth. It is one of the four key elements that make up the human body—alongside hydrogen, oxygen, and nitrogen—and can be found within our atmosphere as carbon dioxide (CO2) and carbon monoxide (CO). As the atmosphere has evolved, the amount of carbon in it has increased due to human activity, primarily from burning fossil fuels. This rise—paired with an uptick in the amount of other heat-trapping greenhouse gases now present in the atmosphere—has warmed the planet significantly, resulting in the climate crisis we are experiencing today.

The evolution of our atmosphere

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The atmosphere, a thin envelope of gases that surrounds our planet and supports life on Earth, evolved in stages. When the Earth first formed over 4.6 billion years ago, its surface was molten, with almost no atmosphere. As it cooled, the atmosphere formed from gases like carbon dioxide and water vapor that spewed from volcanic eruptions. The water vapor eventually condensed to form Earth's oceans. Carbon dioxide began dissolving into shallow seas and allowed cyanobacteria—blue-green algae—to perform oxygen-emitting photosynthesis.

Over 2.4 billion years ago, this oxygen eventually accumulated until the atmospheric composition changed enough to kill off most of the then-existing microorganisms. The methane remaining in the air created a haze. At the time, oxygen was only present in compounds, not as part of the gases that comprised the Earth's atmosphere.

Complex chemical reactions in the early oceans transformed carbon-containing molecules into simple, living cells that did not need oxygen to survive. They used sulfur and other elements as energy sources instead of photosynthesis. Over time, tiny photosynthetic organisms produced enough oxygen to react with the methane in the atmosphere. Eventually, the methane haze cleared, the mix of gases that support the kinds of life forms on our planet today developed, and the sky became blue.

Carbon's role: the carbon cycle

Life is sustained by the carbon cycle. This process traces the path of carbon through different reservoirs on Earth, and the element is constantly moving. Reservoirs effectively store carbon and include our atmosphere, the ocean, plants, and humans.

Carbon plays a crucial role in maintaining the stability of Earth's atmosphere. The carbon cycle balances carbon levels, meaning that the amount of carbon naturally released from reservoirs equals the amount of carbon naturally stored in reservoirs. Maintaining this balance allows the planet to remain hospitable for life. Since the industrial age, human activity has taken carbon out of the ground and burned it, adding more heat-trapping carbon to the atmosphere. This has led to the climate crisis and global warming.

Human impact and global warming

Scientists have repeatedly recognized the dangers of fossil fuels and how they can impact our planet. Due to industrial growth, cheaper costs, and wide availability, we have depended on fossil fuels without proper regulation for over 100 years. In 2022, about 60% of electricity generated in the United States came from fossil fuels, releasing more CO2 into the atmosphere. By relentlessly pumping more fossil fuels into the atmosphere than natural processes can remove, we've increased the Earth's average temperature 1.8°F (1.0°C) since the late 1800s. The annual rate of increase in atmospheric carbon dioxide over the past 60 years is about 100 times faster than previous natural increases, according to the National Oceanic and Atmospheric Administration.

This disruption is already causing a wide range of destructive climate impacts, including increased severity and frequency of storms, widespread flooding, worse wildfires, and more heatwaves. If we do not act decisively and quickly, the system will soon make conditions on Earth even more inhospitable to human life and many other life forms.

Human activity is a distinct marker in data showing how atmospheric carbon dioxide has increased over time.

Chart showing global atmospheric carbon dioxide compared to annual emissions 1751-2022

The relationship between human activity and the dramatically increased amount of carbon in the atmosphere is undeniable. We have disrupted the vital balance needed to sustain our planetary systems as we know them and are already experiencing the fallout.

Restoring the balance

There is still time to curb the worst impacts of the climate crisis. Climate change work that focuses on restoring balance to the carbon cycle is paramount. At WWF, projects like the Renewable Thermal Collaborative and the Climate Business Network take emission reduction to task by directly addressing emissions in industrial thermal applications and among corporate partners to facilitate plans to reduce emissions within supply chains. We also encourage high-integrity carbon interventions through our Nature-Based Solutions Origination Platform. We need urgent and comprehensive action from individuals, communities, businesses, and policymakers to end the era of fossil fuels and restore balance to the carbon systems on our planet.

Learn more about WWF's work on the climate crisis.