What Is Carbon Dioxide (CO2)?

Carbon Dioxide, or CO2, is a chemical compound composed of one carbon atom bonded to two oxygen atoms.

It is an abundant compound found in nature, created when plants and animals convert the energy they get from food into chemical energy. It is a natural byproduct of respiration.

It results when fuel containing carbon is burned (e.g., gasoline or coal) or organic matter decomposes without adequate oxygen present. Carbon dioxide trapped in the atmosphere causes the greenhouse effect and global warming.

It can be sequestered from the atmosphere through the natural carbon cycle, photosynthesis, and absorption.

Carbon Dioxide and Other Greenhouse Gas Emissions in the U.S.


Carbon dioxide has been tagged as the primary greenhouse gas causing climate change, and it has been the subject of a great deal of international debate.

While CO2 is naturally present in the atmosphere because of the Earth's carbon cycle, human activities have altered its normal rate of resupply.

Increasing amounts are being produced by burning coal, oil, and gas for energy and transportation, deforestation, and land-use changes.

According to the U.S. Environmental Protection Agency (EPA), carbon dioxide accounts for about 79% of all U.S. greenhouse gas emissions caused by human activity.


Source: Inventory of U.S. Greenhouse Gas Emissions and Sinks, EPA

Carbon dioxide emissions have largely increased by approximately 90% since 1970.

In its annual Inventory of U.S. Greenhouse Gas Emissions and Sinks report, the U.S. EPA quotes that greenhouse gas emissions from 1990-2021 inventory totaled 6,347.7 million metric tons of CO2 equivalents.

In this trend, a decrease in emissions of 7.0% has been observed from 2020 to 2021, largely due to economic recovery after the start of the COVID-19 pandemic.


According to the U.S. EPA in its 2019 inventory, the following are the primary sources of greenhouse gas emissions in the country:


Source: Inventory of U.S. Greenhouse Gas Emissions and Sinks, EPA


The transportation sector is the largest single source of greenhouse gas emissions in the United States.

Transportation sources account for about 27% of total U.S. greenhouse gas emissions.

This includes CO2 emitted during land, water, or air transportation activities.


The electric power sector is the second-largest contributor to greenhouse gas emissions in the United States.

With a 25% share, this sector emits most of its CO2 through combustion engines that generate electricity for homes and commercial buildings. A significant portion also comes from fossil fuels combusted to produce steam for turbines used to generate electricity.


The industrial sector is the third-largest contributor to greenhouse gas emissions in the United States, accounting for a 24% share.

This sector emits CO2 through processes involved in manufacturing certain chemicals, metals, and materials, generating heat for various energy needs, and combusting fuels to produce steam.

Commercial And Residential

The commercial and residential sectors account for 13% of total U.S. greenhouse gas emissions.

The burning of fossil fuels for heat to be used in homes and businesses and the use of certain products that contain greenhouse gas are sources of emissions in this sector.

Land Use and Forestry

This sector includes natural emissions from plants and soil and clearing forests or agricultural land for use in production.

In the U.S., managed forests and other lands act as a sink which means it absorbs CO2 in amounts that exceed the carbon dioxide released. It offsets about 13% of total GHG emissions.


The agriculture sector accounts for 11% of U.S. greenhouse gas emissions, including methane and nitrous oxide from livestock manure management; enteric fermentation by animals; rice cultivation; agricultural soil management; and equipment used to produce, harvest, or transport agricultural commodities.

Effects of Carbon Dioxide Emissions

At certain concentrations, CO2 can trap heat within Earth's atmosphere and cause an increase in surface temperature or global warming.

Effects directly related to climate change include rising temperatures, changes in rainfall patterns, and extreme weather events.

Higher concentrations of CO2 also lead to acid rain, which causes harm to human health, forests, lakes, and building materials.

Carbon dioxide emissions can even affect the nutritional value of food produced by plants.

Importance of Reducing Carbon Emissions

The need to reduce greenhouse gas emissions is important because even small amounts of CO2 emitted over time greatly impact the environment.

The Intergovernmental Panel on Climate Change (IPCC) has urged world leaders to cut carbon dioxide emissions drastically over the next few decades to avoid the worst impacts of climate change.

Mitigate Climate Change

Different sectors need to work together and meet their targets to reduce greenhouse gas emissions.

Reducing carbon dioxide emissions by decreasing energy consumption will result in less air pollution, improved public health, reduced dependence on foreign oil, and savings that boost the economy.

Improve Public Health

Aside from the ill effects of carbon dioxide emissions on the environment, carbon dioxide can also lead to respiratory illness.

This is especially true in high-density urban areas where carbon dioxide emissions from vehicles and power plants create smog that can irritate the respiratory system.

Boost The Economy

Reducing carbon dioxide emissions positively impacts the economy in several ways.

Energy conservation and switching to renewable energy sources will generate savings passed along to consumers. It will also create new jobs in green technology, such as solar or wind energy industries.

Preserve Biodiversity

Protecting or restoring natural resources like forests and coastal areas is important for mitigating climate change—including its effects on biodiversity loss.

Several strategies like reduced deforestation and improved practices for land use can help reduce carbon dioxide emissions, helping to prevent further loss of natural resources.

Strategies to Reduce Carbon Dioxide Emissions

Energy Conservation

Energy conservation refers to the conscious act of reducing the amount of energy used in any activity.

It can be done even by small efforts like turning off certain appliances when not in use or adjusting the temperature setting on certain devices.

Energy Efficiency

Energy efficiency refers to equipment that has been modified to use less energy while performing the same function.

A typical example of this is switching to LED lights that require less electricity than traditional bulbs.

Switching to Renewable Energy Sources

Renewable energy sources like solar and wind power can produce clean, sustainable energy. They do not release harmful greenhouse gas emissions into the atmosphere.

It will also open opportunities for new jobs in green industries.

Carbon Capture and Sequestration (CCS)

Carbon capture and sequestration (CCS) involves capturing CO2 from power plants before it enters the atmosphere and storing it in a location where it cannot harm the environment.

This technology has been shown to reduce greenhouse gas emissions by up to 80 to 90%. It also makes operations more fuel-efficient and improves air quality around major sources of carbon dioxide emissions.

Reduce, Reuse, Recycle

The sustainable life-cycle management of materials is related to reducing, reusing, and recycling—which is important for reducing carbon dioxide emissions.

These practices help conserve resources so that they are not wasted in production, at home, or in the workplace.

The Bottom Line

Carbon dioxide is a naturally occurring gas that helps regulate temperature while also playing a part in other environmental chemical processes.

Although natural processes release carbon dioxide into the atmosphere at a slow rate, human activity has resulted in excessive amounts of this greenhouse gas being released into the atmosphere—imparting many harmful effects on ecosystems worldwide.

To mitigate these effects, different sectors—including transportation, industry, commercial and residential buildings, and agriculture—need to work together and meet targets for reducing carbon dioxide emissions.


1. What is a greenhouse gas?

A greenhouse gas is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range. Carbon dioxide, methane, and nitrous oxide are all examples of greenhouse gases.

2. Where does carbon dioxide originate?

The main sources of carbon dioxide include fuel combustion at power plants, vehicles emitting exhaust fumes, and industrial processes such as manufacturing cement or producing steel. Residential buildings also create excess carbon dioxide emissions by triggering heating or cooling devices within homes.

3. Why is carbon dioxide considered a greenhouse gas?

When released into the atmosphere, carbon dioxide traps the sun's heat and prevents it from radiating back out to space. This process causes air temperature near Earth's surface to rise, leading to changes in climate patterns.

4. What are other effects due to excess carbon dioxide emissions?

Other harmful effects of excessive amounts of carbon dioxide include ocean acidification which can negatively affect coral reefs and marine life, a sea-level rise that can damage coastal ecosystems, and extreme weather events like floods or heavy rainfall that cause extensive crop loss or property damage.

5. How can we reduce the use of fossil fuels?

Reducing the number of fossil fuels used can help reduce carbon dioxide emissions, but this may increase energy costs in many sectors. To address the issue, governments around the world are making efforts to create alternative sources of energy like solar, wind, and geothermal power—which provide clean forms of renewable energy.

Attend Our Next Webinar

Attend Our Next Webinar

Join our next Sustainable Investing 101 webinar, get our favorite DIY options, and walk through how we build our portfolios.

Watch Now
Get Our Newsletter

Get Our Newsletter

Go a level deeper with us and investigate the potential impacts of climate change on investments like your retirement account.

Talk To A Human

Talk To A Human

Joining a new investment service can be intimidating. We’re here for you. Click below to email us a question or book a quick call.

Ask a Question


Sustainable Investing Topics

View our list of some topics below.