Climate Change: Questions and Answers

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Climate Change: Questions and Answers

Among the greatest concerns currently drawing much attention and studies globally is global warming. One of the main processes that has been associated with global warming is carbon cycle. Carbon cycle refers to the biogeochemical cycle through which carbon gets exchanged between geosphere, hydrosphere, atmosphere, and biosphere of earth, showing how carbon atoms can exist in various compounds at various times as well as be recycled between the environment and organisms (Chen & Wang, 2011). All living organisms are made up of carbon, besides carbon being a component of air, rocks, and ocean (Nielsen & Ho, 2013). Carbon dioxide (CO₂) is trapped/absorbed by producers (plants) for purposes of making their food (glucose) during photosynthesis (Yamaji et al., 2000). Animals consume the producers/plants, thus, passing the carbon compounds down the food chain. A large amount of carbon consumed by animals is exhaled as CO₂ that is formed in them during aerobic respiration (Aulbach & Stagno, 2016). Plants and animals ultimately die. Upon death, decomposers disintegrate the dead plants and animals, allowing carbon to return in their bodies to the atmosphere in the form of CO₂ via respiration. In some circumstances, when a plant dies and are buried in the soil, they may turn into fossil fuels after millions of years (Tian et al., 2018). When human beings burn fossil fuels, carbon quickly enters the Earth’s atmosphere in the form of CO2.

Over time, statistics indicates an alarming concentration of CO₂ in the atmosphere. The current CO2 concentration in parts per million (ppm) is 406.22 ppm as at October 16, 2018 (Tian et al., 2018). Compared to several years before, this level of CO₂ concentration is relatively high. Tian et al. (2018) state that the 402.22 ppm is higher compared to what has ever been registered/observed at any time in the past 450,000 years, noting that during the ice epochs, the level of CO₂ was barely 200 ppm and only rose to 280 ppm during the warmer interglacial epochs. It was in 2013 when the CO2 levels rose beyond the 400 ppm for the very first time in the history of the world (Aulbach & Stagno, 2016).

There are several processes and/or activities that have been shown to contribute to the increasing CO₂ concentration in the atmosphere, among them being human. There are three most abundant CO₂ sources associated with human activities on earth. First is combustion of fuels. Humans burn coal, gas, and oil during power generation, chemical production, industrial sources, through agricultural practices, and petroleum production, processes which produce CO₂ as a byproduct (Nielsen & Ho, 2013). This accounts for about 87% of all man-produced CO₂ emissions (Chen & Wang, 2011). Second is deforestation. 3% of man-produced CO2 emissions come as a result of clearing of forests alongside other land use transformations (10%) and some industrial processes like cement manufacturing (5%) (Yamaji et al., 2000). Third is breathing as well as digesting food.

While there are several mechanisms through which CO₂ is released to the earth’s atmosphere, there are processes that counter the mechanisms (carbon sinks) to keep in check CO₂ concentrations. There are two main natural carbon sinks that function to remove CO₂ from the earth’s atmosphere: plants and oceans. Green plants regulate CO₂ concentration levels in the atmosphere through the photosynthesis. Photosynthesis happens in a plant’s leaves and in the cells of microscopic living organisms. Photosynthesis uses sunlight (sole radiation energy) to convert water and CO₂ into glucose (Nielsen & Ho, 2013). The glucose (sugar) is converted employed in several molecules, like proteins, starch, fats, and enzymes. During photosynthesis, oxygen is released into the atmosphere, a gas that is needed by animals and plants for respiration. This way, CO₂ concentration levels are controlled by plants.

Oceans also serve as a principal carbon sink, absorbing as well as storing carbon. First way through which oceans do this is biological pump. CO₂ enters the oceans through phytoplankton which float on oceans’ surface and suck CO₂ from the atmosphere to aid their photosynthetic processes. These phytoplankton are consumed by other aquatic organisms or they die and sink through the ocean (Chen & Wang, 2011). The dead phytoplankton organisms together cluster as they sink deep into the oceans, minimizing the danger of being consumed and increasing their mass (Yamaji et al., 2000). The last face of the biological pump is when the clusters of dead phytoplankton finally reach the floor of the ocean where they remain for eons, containing CO₂.

Another way through which oceans help in sinking carbon is via CO₂ diffusion (solubility pump). When CO₂ pressure within the atmosphere is higher compared to that of the water surface, the atmospheric CO₂ dissolves/diffuses into the ocean (Yamaji et al., 2000). Another way the oceans work is that calcium carbonate is a fundamental ingredient that oysters, clams, coral and other hard bodied marine creatures rely upon to create/make their hard shells. The shell is produced when CO₂ combines with calcium that has initially diffused/dissolved in seawater (Chen & Wang, 2011). When these marine organisms die, their shells and body parts sink deep into the ocean, even to the seafloor, therefore, burying or hiding carbon (Nielsen & Ho, 2013). Over time, these organisms create deposit layers that are rich in calcium carbonate at the ocean floor. After several millions of years, these carbonates create pressure and heat that causes them to convert into sedimentary rocks, like marble, limestone, and chalk (Aulbach & Stagno, 2016).

As aforementioned, human activities contribute to the increasing levels of CO₂ concentration in the atmosphere. One of the human activities that leads to the increase is deforestation. Deforestation contributes to the increase in CO₂ levels in several ways. One of the main ways is that it contributes to fewer trees to help “clean” the atmosphere. Plants and trees, generally, produce energy for their growth through photosynthesis. Using water, CO₂, and light, a plant generates energy in sugar form and discharges oxygen into the atmosphere. This way, plants and trees reduce the level of CO₂ concentration in the air (Tian et al., 2018). However, when deforestation occurs, the number of trees and plants is reduced, implying a reduction in the agents of air purification (Nielsen & Ho, 2013). Similarly, deforestation leads to less oxygen produced. Plants and animals alike use oxygen for respiration process, during which process they produce CO₂. However, when trees are cut down, the levels of CO₂ rise since less of it removed from the air (Chen & Wang, 2011). Thus, deforestation increases the CO₂ levels in the air.

Apart from than CO₂, other greenhouse gases that are raising concerns globally are water vapour, methane, nitrous oxide, ozone, chlorofluorocarbons, and hydrofluorocarbons. According to Yamaji et al. (2000), the concentrations of these greenhouse gases have been all increasing substantially, making current concentrations higher than those in 450,000 years. For instance, Aulbach and Stagno (2016) note that methane’s concentration in the atmosphere has increased by more than twice since the pre-industrial periods, standing at about 1,800 ppb as at 2014 and 2015 statistics. Nielsen and Ho (2013) state that over the last 800,000 years, nitrous oxide’s concentration in the air hardly surpassed 280 ppb. However, the concentrations have increased as from 1920s, reaching 328 ppb in the year 2015. This increase has significantly and statistically been attributed to agriculture. These increases in the greenhouse gases’ concentrations have been attributed to increased human activities that involve burning of fossil fuels.

From the data and statistics above, carbon cycle bears warning signs to humanity. The increase in CO₂ concentration is fast increasing global warming, which a great life-threating phenomenon. (2017) study employed, there are very little room for generalizing the study’s findings.