The Planet’s Carbon Budget: Sequestration vs. Production

Planet Earth experiences a majestic carbon cycle, with carbon dioxide (CO₂) being emitted and absorbed through various natural processes and human activities. Understanding the balance between these emissions and sequestrations is crucial for addressing climate change.

CO₂ from human activities:

• Fossil Fuel Combustion: Burning coal, oil, and natural gas for energy and transportation is the largest source of anthropogenic CO₂ emissions.
  • Coal: The combustion of coal for electricity and heat production remains a major source of CO₂ emissions. In 2024, emissions from coal combustion increased, particularly in countries like India.¹
  • Oil: Oil consumption, especially in the transportation sector, contributes significantly to CO₂ emissions. The rebound in global flights and increased transportation activities have led to a rise in oil-related emissions.²
  • Natural Gas: Natural gas is used for electricity, heat production, and industrial processes. Its combustion releases CO₂, adding to the global emissions tally.
• Cement Production and other Industrial Processes: The chemical process of converting limestone into clinker releases significant amounts of CO₂. In 2024, emissions from cement production continued to be a substantial part of industrial CO₂ emissions.
• Land Use Changes: Deforestation and forest fires, exacerbated by droughts, particularly in regions like the Amazon, have led to a significant rise in CO₂ emissions from land use changes. In 2024, these emissions increased by 13.5% to 4.2 billion tons in 2024.³

Combining emissions from the above sources, the total global CO₂ emissions in 2024 were approximately 41.6 billion tons.⁴ Divided by 8.2 billion humans averages at 5 tons each.

CO₂ produced as part of natural processes:

Natural sources of CO₂ include respiration from plants and animals, decomposition of organic matter, and volcanic activity. However, these emissions are historically balanced by natural sequestration processes, maintaining a relatively stable atmospheric CO₂ level over geological timescales.

CO₂ Sequestration Mechanisms

The planet employs several mechanisms to absorb CO₂:

• Soil: Currently, soils remove about 25% of the world’s fossil fuel emissions each year, though human activities, particularly certain agricultural practices, have led to significant carbon losses from soils. It’s estimated that soils have lost 50% to 70% of the carbon they once held due to land conversion and management practices. This loss has contributed to about a quarter of all man-made global greenhouse gas emissions.⁵ Implementing regenerative agricultural practices, such as cover cropping, reduced tillage, and organic amendments, can enhance soil carbon sequestration. Studies suggest that restoring and protecting the world’s soils could offset up to 5.5 billion tonnes of greenhouse gases annually, which is comparable to the current annual emissions of the United States.⁶
• Forests and Terrestrial Ecosystems: Globally, forests absorb nearly 16 billion metric tons of CO₂ annually.⁷ Forests and land ecosystems typically absorb nearly a third of annual human-caused emissions. However, in 2023, severe droughts in the Amazon and record wildfires in Canada significantly reduced their carbon uptake.⁸
• Oceans: The oceans absorb about 31% of the CO₂ emissions released into the atmosphere⁹. However, ocean acidification, a consequence of increased CO₂ absorption, poses a threat to marine ecosystems.

CO₂ can react with sea water – with a molecule of (double negative) bicarbonate and produces two (negative) bicarbonate molecules – but this made the sea 30x more acidic¹⁰.

It’s important to note that these figures vary based on factors such as environmental changes, land use practices, and the health of ecosystems. Additionally, recent studies have indicated that the capacity of natural carbon sinks may be declining due to factors like wildfires, droughts, and other climate-related impacts.¹¹

---

Balancing Emissions and Sequestration

Before human industrial activity, Earth’s natural CO₂ emissions (from respiration, decomposition, and volcanoes) were approximately equal to natural sequestration, maintaining a stable atmospheric balance. However, human activities have added, as listed, an extra 41.6 billion metric tons of CO₂ annually. While natural processes still absorb about half of this excess CO₂, the remaining amount continues to accumulate in the atmosphere, driving climate change.

To prevent further increases in atmospheric CO₂, human emissions must be reduced to a level where they match natural absorption. Current natural sequestration processes absorb approximately 20 billion metric tons per year, meaning that to achieve balance, human-caused emissions must be reduced from 41.6 billion to about 20 billion metric tons annually. This would require cutting emissions by more than 50% as soon as possible.

8.2 billion humans producing 21.6 billion tons of carbon dioxide equates to 2.6 tons each.

The Paris Agreement, which aims to limit warming to below +2°C¹² (ideally +1.5°C, but 2024 temperatures increased by 1.6°C above the 1850-1900 average¹³).

Sources

1. Rebound of airline flights pushes up global carbon dioxide emissions, The Times, 2024-11-13 ↩︎
2. Ibid. ↩︎
3. Global CO2 emissions to hit record high in 2024, report says, Reuters, 2024-11-13 ↩︎
4. Ibid. ↩︎
5. Can Soil Help Combat Climate Change? Columbia Climate School, 2018-02-21 ↩︎
6. Restoring soils could remove up to ‘5.5bn tonnes’ of greenhouse gases every year, CarbonBrief, 2020-03-16 ↩︎
7. Global forest carbon storage, explained, Woodwell Climate Research Center, 2024-03-17 ↩︎
8. World’s forests failed to curb 2023 climate emissions, study finds, Reuters, 2024-07-29 ↩︎
9. Quantifying the Ocean Carbon Sink, National Centers for Environmental Information, 2024-07-19 ↩︎
10. The Ph of the sea has reduced by 0.1, meaning 30x more acid. ↩︎
11. Trees and land absorbed almost no CO2 last year. Is nature’s carbon sink failing? The Guardian, 2024-10-24 ↩︎
12. Climate: Greenhouse gas emissions are too high, pushing planet toward +3.1°C warming, Le Monde, 2024-10-24 ↩︎
13. 2024 was the hottest year on record, scientists say, Reuters, 2025-01-10 ↩︎