Carbon dioxide (CO2) is an important trace gas in the earth's atmosphere that constitutes about 0.04% of the total atmospheric gases. The gas is odorless and tasteless. This small concentration has a big impact on the planet. Despite the relatively small concentration of CO2, it is a potent greenhouse gas and plays a vital role in regulating the Earth's surface temperature. According to the National Oceanic (NO) and Atmospheric Administration (AA), without the warming of the planet provided by carbon dioxide and other so-called greenhouse gases, the earth's average temperature would have fallen below freezing point. Greenhouse gases are naturally occurring gases that pose no problem when they are in balance in the atmosphere but when their concentration is high, the system becomes unbalanced. Larger emissions of greenhouse gases lead to increase concentrations in the atmosphere. The concentrations are measured in parts per million and parts per billion, or even parts per trillion. Reconstructions indicates that the concentrations of CO2 in the atmosphere have varied, changing from as high as 7,000 ppm during the Cambrian period that is about 500 million years ago to as low as 180 ppm during the Quaternary glaciation of the last 2 million years.Greenhouse gases in the atmosphere have increased steadily since 1958 and was primarily due to Industrial Revolution. Since Industrial Revolution, human activities have caused an increase in the concentration of unnatural sources of greenhouse gases into the atmosphere, making the system to become unbalanced.The most commonly known greenhouse gases are; CO2, nitrous oxide, CH4, and water vapor. All these gases occur naturally in the atmosphere. Emissions from human sources have caused their concentration to increase to a level that is no longer sustainable. Each of these gases can remain in the atmosphere for a very long period of time, ranging from a few to thousands of years. This means the amount of these gases that is measured in the atmosphere is roughly the same all over the world, regardless of the source of emission. Enormous amounts of Carbon dioxide are continually exchanged between the atmosphere, oceans and land. Land and marine plants grow, die and then decay, leading to the circulation carbon-rich waters in the ocean. The different sources of Carbon dioxide emissions to the atmosphere can be of natural or anthropogenic (man-made).
Natural CO2 sources
Natural sources of CO2 account for the majority of Carbon dioxide gases released in the atmosphere. The greatest annual amount of CO2 is provided by Oceans. The carbon dioxide that is released to the atmosphere from natural sources is removed in equal amount by other natural occurrences. These natural Carbon dioxide sinking processes includes; photosynthesis in plants and dissolution in water. This therefore means, the natural production and removal of carbon dioxide from the atmosphere keeps the system well balanced. Natural sources of Carbon dioxide include decay of organic matter, animal, respiration, forest fires, emissions from volcanic eruptions and ocean release.
a.) Animal respiration
Animals return carbon dioxide and water vapor to the atmosphere during respiration. This accounts to about 28.56% of the natural carbon dioxide emission in the atmosphere. Carbon dioxide is a byproduct of the chemical reaction that both plants and animals use to produce their energy. The combination of glucose with oxygen from the atmosphere produces energy for organisms through the process of respiration. During this process, glucose and oxygen are changed into energy and Carbon dioxide, Carbon dioxide is then released to the atmosphere.
b.) Volcanic eruptions
The most common volcanic gases include; sulfur dioxide, carbon dioxide, and water vapor. Volcanic eruptions accounts for about 0.03% of the natural Carbon dioxide emissions. During volcanic eruptions magma, ash, dust and gases are released from deep below the Earth's surface.
c.) Ocean release
The oceans contain dissolved CO2, which is released into the air at the sea surface. This is the largest natural source of carbon dioxide emissions in the atmosphere and accounts to about 42.84%.
Man-Made (Anthropogenic) CO2 Sources.
Human activity releases carbon dioxide into the atmosphere. Anthropogenic CO2 sources include power generation, industrial sources, transportation, chemical production, agricultural practices, petroleum production, burning of forest and deforestation. Many of these source types burn fossil fuels which are the leading cause of CO2 emissions. As stated by the Environmental Protection Agency (EPA), humans have contributed to the concentration of carbon dioxide in the atmosphere since the start of the industrial revolution. Human sources of CO2 emissions are much smaller than natural emissions but they have disturbed the natural balance that existed for many thousands of years before human influence. This can be explained by the fact that in a balanced system, the number of input is equal to the number of output. This means in a natural system the same quantity of carbon dioxide produced from natural sources could be removed by Carbon dioxide sinking processes thereby keeping the system balance. Unfortunately, human sources of Carbon dioxide upset the natural balance by adding more carbon dioxide to the atmosphere without removing any.
a.) Power generation
Apart from Canada and France, almost all the industrialized nations get the majority of their electricity from the combustion of fossil fuels. The generation of electricity and heat is the economic sector that produces the largest amount of man-made carbon dioxide emissions. During combustion, carbon from fossil fuels combine with oxygen in the air to produce carbon dioxide and water vapor.
b.) Transportation
This sector is the second largest source of man-made carbon dioxide emissions in the atmosphere after power generation. According to International Energy Agency (IEA) 2010, the transportation of goods and people around the world produced 22% of fossil fuel related carbon dioxide level in the atmosphere. Also, IEA estimated that the road transport accounts for 72% of the Carbon dioxide emitted in this sector, marine transport accounts for 14% while the global aviation accounts for 11% of the carbon dioxide level in the sector.
c.) Industrial sources
This sector is the third largest source of man-made carbon dioxide emissions in the atmosphere. The industrial sector includes construction, mining, manufacturing, and agriculture companies. These industries use fossil fuels to generate heat and steam needed at various stages of their production. For example, a cement industry burns fossil fuel to generate the 14500C heat needed to convert limestone into cement. And in addition carbon dioxide is the byproduct of the chemical transformation of calcium oxide and limestone into cement. Other industrial processes that lead to the emission of Carbon dioxide in the atmosphere include; steel production and the manufacture of petrochemical products.
d.) Burning of forest and deforestation
The burning of forests not only releases carbon dioxide in the atmosphere, but cutting down of trees can also affect the Carbon dioxide absorption. Vegetation acts as Carbon sink by absorbing Carbon dioxide from the atmosphere during the process of photosynthesis. This process converts the Carbon dioxide into to carbon which is stored within all plants. Therefore, fewer vegetation means more Carbon dioxide level in the atmosphere.When trees are burned, this organic Carbon is released into the atmosphere as Carbon dioxide, and in so doing it becomes a carbon source rather than a carbon sink. Since deforestation reduces the amount of trees, the amount of Carbon dioxide removed by the Earth's forests is also reduced. This is because when deforestation is carried out to create new agricultural land, the new crops that replace the trees also act as a carbon sink, but these crops are not as effective as forests.
We can conclude from the above mentioned points that humans are the main cause of carbon dioxide in the atmosphere. As for nature, it has a natural way of recycling its emitted carbon dioxide.
Greenhouse gas effect of CO2
Greenhouse gases emitted from natural sources possesses no challenges to natural processes as well as to human life. Greenhouse gases allows heat from sun to penetrate the atmosphere, where it is absorbed by the Earth’s surface or it is radiated out and reflected back to Earth by greenhouse gases in the atmosphere, including carbon dioxide (CO2). Without this, the Earth would have been a cold and hostile planet, and likely be uninhabitable. Carbon dioxide plays a significant role by providing the relatively warm temperature that the planet enjoys. Carbon dioxide is believed to have played an important role in regulating Earth's temperature since its origin. Atmospheric concentrations of greenhouse gases are determined by the balance between sources and sinks. Increases in Carbon dioxide have other effects apart from global warming such as ocean acidification, acid rain, ozone depletion and changes to plant growth as well as nutrition levels.
Carbon dioxide emissions and trends
The primary greenhouse gas emitted through human activities is Carbon dioxide (CO2). This gas is naturally present in the atmosphere as part of the Earth's carbon cycle which is the overall Carbon circulating among the atmosphere, soils, oceans, animals and plants.Human activities are altering this cycle both by adding more CO2 to the atmosphere as well as influencing the ability of natural sinks to remove CO2 from the atmosphere. In the United States, Carbon dioxide concentration have increased by about 9% between 1990 and 2014. Between this period, the increase in CO2 emissions corresponded with the increased use of energy by an expanding economy and population, as well as an increase growth in emissions from electricity generation.
Reducing Carbon Dioxide Emissions
The most common way to lower Carbon dioxide emission by humans is to reduce the consumption of fossil fuel and use renewable energy that produces little or no Carbon dioxide. Carbon dioxide emission to the atmosphere can be reduced by planting trees that uses sun light energy to converts the atmospheric CO2and water to manufacture its own food and in the process release O2 which is very useful to humans. Another option for reducing Carbon dioxide emission is to use less air conditioning and heating in the house.
It is also important to properly recycle the disposable items after use. This may limit the Carbon dioxide emission in the atmosphere. On average over the past fifty years, about 25% of total Carbon dioxide emissions were absorbed by the ocean making sea water more acidic. About 30% was taken up on land, as a result of increased plant growth stimulated by rising atmospheric CO2. The remaining 45% of emissions accumulated in the atmosphere.
Carbon dioxide as a main course to Global Warming
Global warming is primarily an environmental problem resulting from very high concentrations of carbon dioxide in the atmosphere. Climatic warming or cooling occurs as a result of changes in the flow of energy through the system. Atmospheric warming results from increases in atmospheric carbon dioxide level and other long-lived greenhouse gases as methane, nitrous oxide and chlorofluorocarbon. Human emissions are increasing the carbon dioxide level in the atmosphere, and as such increasing the greenhouse effect. Some of the heat reaching the earth’s surface is trapped by greenhouse gases in the atmosphere, including carbon dioxide (CO2). Since the Industrial Revolution, the burning of fossil fuel as well as natural gas has emitted about 500 billion tons of Carbon dioxide, about half of which remains in the atmosphere. And today CO2 is the biggest factor responsible for global warming. This is because the more carbon dioxide level in the atmosphere, the more amount of heat will be trapped and the warmer will be the planet. Warming can cause sea level rise, the expansion of areas affected by drought, increasing level of severe heat waves, shifting precipitation patterns, and more intense precipitation events. To avoid the level of global warming which is considered dangerous we need to achieve major reductions in global CO2 emissions in the next 40 years. Taking a closer look at the problem of global warming, scientists have identified that natural climate drivers are short-lived processes, while human emissions are primarily responsible for the rapid rise in temperatures that we have seen over the last century and what we are witnessing today.