What Causes Carbon Dioxide Emissions in the Air?

Carbon dioxide (CO₂) is a greenhouse gas that is released into the atmosphere through human and natural activities. Humans primarily contribute to CO₂ emissions by burning fossil fuels like coal, oil, and natural gas. This has caused a significant increase in atmospheric CO₂ levels, which now stand at 150% of what they were in 1750, exceeding the levels at the end of the last ice age 20,000 years ago.

In recent years, CO2 concentrations have surpassed 400 parts per million (ppm) in the mid-troposphere. As of June 2023, the values have reached to 421 ppm. 

Carbon dioxide emissions have significant implications for the climate system. Elevated CO₂ concentrations contribute to the greenhouse effect, trapping heat in the atmosphere and leading to global warming. This, in turn, causes hotter temperatures, melting ice, rising sea levels, altered weather patterns, and disruptions to ecosystems.

Understanding the impact of CO₂ on climate change is crucial. That is why we wrote this informative article on what causes carbon dioxide emissions in the air. Keep on reading to learn more.

What are carbon dioxide emissions?

Carbon dioxide (CO₂) is a colorless, odorless, and non-poisonous gas that is naturally occurring. This gas comes from numerous sources and is produced for example through the combustion of carbon, respiration of living organisms, and photosynthesis. This gas is also emitted as a byproduct of fossil fuel combustion, biomass burning, land use changes, and industrial processes.

CO₂ is a greenhouse gas, affecting the Earth’s radiative balance and contributing to global warming and climate change. It is the principal anthropogenic greenhouse gas and serves as the reference gas for measuring the Global Warming Potential of other greenhouse gases.

What is the highest source of carbon emission?

Since the Industrial Revolution, human activities have been responsible for a substantial increase in carbon dioxide emissions. The primary source of these emissions include the burning of fossil fuels (oil, coal, and gas).

The burning of fossil fuels accounts for approximately 87% of human-produced carbon dioxide emissions. The remaining emissions originate from activities like forest clearing and land use changes (9%), as well as certain industrial processes like cement manufacturing (4%).

Fossil fuels contain carbon that has been stored underground for millions of years. When these fuels are burned for energy production, transport, or industrial processes, carbon dioxide is released into the atmosphere as a byproduct.

Over the past century, global carbon emissions from fossil fuels have witnessed a significant rise. Since 1900, there has been a substantial increase. Notably, since 1970, CO2 emissions have surged by approximately 90%.

What causes carbon dioxide emissions in the air?

By now, most of us have become keenly aware that carbon emissions (CO₂ emissions) are accumulating in the Earth’s atmosphere. These increased carbon emissions are causing global temperatures to increase and are changing the climate of our planet. In order to really understand the impacts of carbon emissions, we must first understand where they originate from, both natural and human sources.

Human causes of carbon emissions

Burning the stored energy of fossil fuels over the last 150 years has allowed humanity to develop many of the amazing things that we have in our modern world today. However, much of this development and fossil fuel use has been at a rate far beyond the Earth’s ability to compensate for all of the carbon emissions that we have been producing.

In fact, human activities produce about 135 times the carbon dioxide that volcanoes do every year, with volcanic CO₂ emissions producing about 0.13 to 0.44 billion metric tons per year, and human activity producing more than 35 billion metric tons per year [1].

It has been estimated that CO₂ levels in the atmosphere have increased from 280 ppm prior to the mid-1700s to the current levels of more than 421 ppm [2].

#1 Burning fossil fuels

Fossil fuels release carbon dioxide when they are burned for various purposes, such as generating electricity, powering vehicles, and providing heat for industrial processes and residential use. Fossil fuels contain stored carbon that has accumulated over millions of years from ancient plants and organisms.

When we burn these fossil fuels to extract their energy, the carbon stored within them combines with oxygen in the air during the combustion process. This chemical reaction produces carbon dioxide as a byproduct.

#2 Deforestation

Deforestation involves the clearing and removal of forests and other natural vegetation for agriculture or urban development. When trees are cut down or burned, the carbon stored in these plants is released into the atmosphere in the form of carbon dioxide.

Forests are essential carbon sinks, meaning they absorb and store carbon dioxide from the atmosphere through the process of photosynthesis. When trees are removed, this capacity for carbon sequestration is diminished, and the ability of the remaining vegetation to absorb CO₂ is reduced.

The impact of deforestation on carbon dioxide emissions is substantial. It is estimated that deforestation and land-use changes account for about 10% to 15% of global carbon dioxide emissions each year.

Conserving forests and reforesting areas that have been deforested are crucial steps in reducing carbon dioxide emissions and mitigating the impacts of climate change. By preserving existing forests and implementing sustainable land-use practices, we can maintain vital carbon sinks and contribute to the global effort of combating climate change.

#3 Agriculture

Agricultural activities contribute to carbon emissions in various ways, mainly through the release of CO₂ and other greenhouse gases during different farming practices.

Here are some ways agriculture causes carbon dioxide emissions:

• Land use changes: Converting natural ecosystems, such as forests and grasslands, into agricultural lands releases carbon stored in trees and vegetation. This process contributes to deforestation and results in the loss of vital carbon sinks.
• Soil management: Certain soil management practices, such as plowing or tilling, can lead to the release of CO₂ from the soil. These practices expose organic matter to oxygen, accelerating the decomposition process and increasing carbon dioxide emissions.
• Biomass burning: In some agricultural practices, biomass is burned to clear fields or for waste management. The burning of biomass releases carbon dioxide and other greenhouse gases into the atmosphere.

Did you know? Agriculture also plays a crucial role in sequestering carbon. Certain farming practices, such as agroforestry, cover cropping, and conservation tillage, can enhance carbon sequestration in the soil and vegetation.

Efforts to reduce carbon emissions in agriculture include adopting sustainable land management practices, optimizing fertilizer use, promoting more efficient irrigation methods, and transitioning towards climate-smart and regenerative agricultural practices.

By balancing emissions with sequestration, sustainable agriculture can become a part of the solution to address climate change and ensure food security in a changing world.

#4 Industrial processes

Industrial activities release CO₂ primarily through the burning of fossil fuels for energy production and various manufacturing processes.

Many industries rely heavily on fossil fuels to meet their energy needs. These fuels are burned in factories, and other industrial facilities to generate electricity, heat, and steam. The combustion process releases CO₂ as a byproduct.

Cement is a crucial component in construction, and its production involves a chemical process known as calcination. During calcination, limestone (calcium carbonate) is heated to produce lime (calcium oxide), releasing carbon dioxide as a result.

Cement production is a significant source of industrial CO2 emissions.

Certain industrial processes, such as steel production, chemical manufacturing, and refineries, can also release carbon dioxide as part of their operations. These emissions can come from various chemical reactions and energy-intensive processes.

Industries often rely on transportation and shipping to move goods and raw materials. These activities typically involve the burning of fossil fuels in vehicles, ships, and airplanes, resulting in additional CO₂ emissions.

Many industries are working to adopt cleaner technologies and practices to reduce their carbon footprint. Transitioning to renewable energy sources, improving energy efficiency, implementing carbon capture and storage (CCS) technologies, and adopting more sustainable manufacturing processes are some of the strategies being pursued to decrease industrial emissions and promote a greener and more sustainable industrial sector.

#5 Waste management

Yes, even the waste can release carbon dioxide emissions contributing to greenhouse gas concentrations in the atmosphere. Different types of waste and waste management practices do result in the release of this gas.

Incineration, a waste disposal method that involves burning waste, can release carbon dioxide into the atmosphere. Although it is considered a form of energy recovery, incineration still results in carbon dioxide emissions and can contribute to air pollution.

In some places, waste, including plastic and other materials, is burned openly or in uncontrolled fires. Such practices release carbon dioxide and other harmful pollutants into the air.

Decomposition of Organic Waste: Organic waste, if not managed properly, can also decompose in natural environments or improper disposal sites, leading to carbon dioxide emissions.

#6 Other energy intensive activities

Certain energy-intensive processes like metal smelting and refining also release carbon emissions during their operations.

Natural sources of carbon emissions

While most of the carbon emissions that are changing our climate are produced through human activity, there are also natural sources of carbon emissions.

#1 Respiration

Animals and plants release carbon dioxide as a byproduct of respiration. Just like we exhale carbon dioxide when we breathe, animals and plants also respire, emitting CO₂ into the atmosphere.

But here’s something interesting: carbon dioxide is not just a “bad guy”! In nature, carbon dioxide is used by trees and other green plants during a process called photosynthesis. They absorb carbon dioxide from the air, along with sunlight and water, and turn it into energy to grow and survive. So, carbon dioxide is like a building block for plants!

And it doesn’t stop there! When animals eat plants, they absorb some of that carbon dioxide too. This creates a natural cycle where carbon dioxide moves between plants and animals, keeping everything in balance.

#2 Decomposition

During decomposition, various microorganisms, such as bacteria and fungi, break down dead plants, animals, and other organic matter. As these organic materials are broken down, the carbon they contain is released in the form of carbon dioxide. This happens because the microorganisms respire, just like humans and animals do, and CO₂ is produced as a byproduct of their life processes.

The decomposition process is crucial for nutrient cycling in ecosystems. It helps recycle essential elements like carbon, nitrogen, and phosphorus, allowing new plants and organisms to use these nutrients for growth and survival. It also plays a vital role in breaking down dead organic matter and returning carbon to the atmosphere, completing the carbon cycle.

#3 Soil respiration

Soil respiration, also known as soil breathing, is the process by which microorganisms, plant roots, and soil-dwelling organisms release carbon dioxide into the atmosphere.

Soil respiration occurs because of biological activity in the soil. Microorganisms, such as bacteria and fungi, break down organic matter, like dead plants and animals, through decomposition. This decomposition process releases carbon dioxide as a byproduct of respiration. Additionally, plant roots also respire and release CO₂ into the soil, which can later be released into the atmosphere.

The amount of carbon dioxide released through soil respiration varies based on factors such as temperature, moisture, and the amount of organic matter present in the soil. In warmer conditions with higher moisture levels, soil respiration tends to increase, leading to higher CO₂ emissions.

#4 Ocean outgassing

While the oceans play a vital role in absorbing carbon dioxide from the atmosphere, they can also act as a source of CO₂ emissions under certain conditions.

Here’s how it works:

The oceans act as a massive carbon sink, absorbing a significant amount of carbon dioxide from the atmosphere. CO₂ dissolves in seawater, forming carbonic acid, which is then converted into bicarbonate and carbonate ions. This process, known as oceanic carbon uptake or ocean carbon sequestration, helps regulate the concentration of carbon dioxide in the atmosphere.

However, the oceans are not only a one-way carbon sink. In some regions and under specific circumstances, they release carbon dioxide back into the atmosphere. This occurs when water becomes warmer or when there are changes in ocean circulation patterns.

As the water warms, its capacity to hold dissolved gases decreases, leading to the release of CO₂ into the air. Additionally, areas with upwelling currents can bring deep ocean waters rich in dissolved carbon to the surface, contributing to outgassing.

The balance between carbon dioxide absorption and outgassing in the oceans is critical for maintaining the overall carbon cycle and regulating atmospheric carbon dioxide levels. While the oceans are currently absorbing a significant portion of human-generated CO₂ emissions, they also have the potential to release CO₂ in response to changes in temperature and circulation patterns.

#5 Volcanic activity

When volcanoes erupt, molten rock called magma rises to the surface. This magma contains dissolved gases, including water vapor, carbon dioxide, sulfur dioxide, and others. As the magma reaches the surface, the pressure decreases, causing the gases to be released in the form of volcanic emissions.

The amount of CO₂ emitted from volcanic activity is relatively small compared to human-induced emissions. The total annual carbon dioxide emissions from volcanic eruptions are estimated to be around 200 million to 300 million metric tons, which is significantly lower than the billions of metric tons emitted by human activities each year.

#6 Wildfires

Wildfires are a natural source of carbon emissions. When wildfires burn through vegetation and organic matter, the carbon stored in those materials is released in the form of CO₂.

The process of burning during wildfires is essentially combustion, similar to burning fossil fuels or other organic matter. As the fire consumes trees, plants, and other vegetation, the carbon within these materials combines with oxygen in the air to produce carbon dioxide. This process releases the stored carbon back into the atmosphere.

Wildfires are a natural part of many ecosystems and have occurred throughout the Earth’s history. However, their frequency and intensity can be influenced by climate change, land management practices, and human activities. In recent times, wildfires have become more severe and widespread in some regions due to a combination of these factors.

The carbon dioxide released from wildfires is part of the natural carbon cycle. In healthy ecosystems, the carbon released during wildfires is eventually reabsorbed by new vegetation as it regrows. However, when wildfires are too frequent or intense, it can overwhelm the natural carbon balance, leading to a net increase in atmospheric carbon dioxide levels.

Natural carbon sinks keep the balance

The natural sources of carbon emissions are part of the Earth’s carbon cycle, the planet’s natural systems, such as forests, oceans, and soil, have mechanisms to absorb and balance these emissions.

The carbon cycle involves a delicate balance between carbon emissions and carbon sinks, which help regulate carbon dioxide levels in the atmosphere.

The carbon “sinks” of the Earth are like big storage units for carbon dioxide. They can absorb and store much of the carbon dioxide produced by natural sources. Under normal conditions, these natural “sinks” are more than capable of handling all the carbon dioxide that’s produced.

So, don’t worry, nature has its own way of taking care of carbon emissions. It’s essential for the plants and other photosynthetic organisms to have carbon dioxide for photosynthesis, and the Earth’s natural systems are great at storing and using it properly.

However, since the Industrial Revolution, mankind has been burning the stored carbon within fossil fuels at a very fast rate, changing the landscape, and we have exceeded the capacity of these natural systems to compensate for our increased levels of carbon emissions.

To see where most of the global carbon emissions are generated and how they have increased from 1961-2017, check out the Global Carbon Atlas.