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There has been growing concern over environmental issues: Be it in politics, economics, boardrooms, streets, or education institutions, environmental issues have taken a front seat. One issue that comes up when addressing environmental issues is global warming. Almost everyone has an opinion about global warming. The main source of opinions on this matter is the scientific debate. On many occasions, scientists have been warning that global warming is here and its real and its effects are intensifying. It has been predicted that the greatest sun storm is about to occur. On the other hand, there are some scientists who believed that the intensity of global warming is not as huge as it is professed. Many factors have therefore been added on the debate. Additionally, one question of the debate is whether or not human beings are responsible for global warming. This paper therefore seeks to examine the causes of climate change and present the views of both the proponents and opponents.
It is necessary that people understand the meaning of global warming before any arguments about its causes are addressed. According to Maslin (2007), global warming refers to a rise in the earth’s temperature. It occurs when greenhouse gases accumulate in the atmosphere. These gases that comprise of carbon dioxide, chlorofluorocarbons, methane, water vapor and nitrous oxide trap light and heat from the sun within the atmosphere. As a result, the temperature of the earth rises: The sun rays cannot be reflected back causing what is referred to as the greenhouse effect. Sometimes the greenhouse effect is important, because it helps to keep the earth warm for the living things to survive. However, if the temperature is more than normal, the earth can get warmer and make both the flora and fauna to die. Global warming also melts the glacier on mountain tops, especially in the Polar Regions leading to a rise in the sea levels. Eventually, the water covers the low islands killing most of the animals and plants on the island. It has also resulted to destruction of forests through forest fires and acid rain among other adverse effects.
Ultimately, the most fundamental question is whether or not the observed warming of the planet that has been experienced in the last thirty years is caused by human activities or natural causes. At first glance, some people might jump into conclusion that human beings are responsible for global warming. After all, human acidities like burning fossil fuel release carbon dioxide, one of the greenhouse gases that lead to global warming. However, in seeking to understand the global warming phenomenon, it is important to also consider the natural causes that warmed the earth before the industrial revolution and even before the existence of man on the earth because records show that global warming can be traced back to the past one million years.
Human Causes of Global Warming
Maslin (2007) affirms that there are several human activities that contribute to the release of greenhouse gases into the atmosphere. Starting with the most common, carbon dioxide, its largest source is combustion of fossil fuels. Human beings mostly depend on fossil fuel for energy in industries, transport sector and even as a source of domestic fuel. For instance, when coal is burned to produce energy, molecules of CO2 are released into the atmosphere in the form of smoke. Additionally, with the increasing growth of the transport sector, more fossil fuel is being burned by locomotives, such as aircrafts, buses, trains, cars, and lorries. The fumes of smoke released by running engines comprise of carbon dioxide as one of the gases.
The process of electricity generation through burning of coal, especially in developed countries, such as the US releases so much CO2. It is estimated that about 41% of the total CO2 emitted in the country comes from electricity generation plants. The process of cement manufacturing is a non-energy source of CO2. When the raw material of cement, limestone is heat, it breaks down to release CO2 as one of the by-products. The land use changes conducted by human beings are also a big source of CO2. For instance, general deforestation leads to the accumulation of the CO2 in the atmosphere (Maslin, 2007). The proportion of the world’s total forest cover has reduced tremendously. These activities are estimated to have contributed to close to 1.7Pg C every year in the tropics. The burning of biomass also emits so much CO2 into the atmosphere thus causing global warming.
Another green house gas released by human activities is nitrous oxide. According to Stern, et al (1992), the most common way by which human beings release this gas is through the use of nitrogen fixing fertilizers to boost their agricultural activities. Through the process, the fertilizer volatilizes into oxides of nitrogen and ammonia. In the long run, it is re-deposited in the soil as nitric acid, ammonium and oxides of nitrogen. Subsequent activities, such as leaching and surface runoff of applied nitrogen can also result to indirect addition of nitrous oxide into the atmosphere. As much as the fertilizers help farmers to crease production, nitrogen is taken up by plants and later released into the atmosphere. Similarly, human activities that entail burning of biomass result into the addition of N2O into the atmosphere causing global warming.
Coal fire plants produce the majority of N2O followed by passenger cars and trucks with catalytic converters. Industries that are involved in the production of nylon papers and nitric acid also release N2O. Nitric acid is used mainly as a feedstock in the production of synthetic commercial fertilizer. Additionally, it is the main component in production of explosives that are used in quarrying and wars. Production of adipic acid is responsible for about 1% of the total N2O produced in the US. Adipic acid is not only used in nylon production, but also as a flavor enhancer in some foods (Stern, et al., 1992). Most of the nitric acid the US produces is manufactured through the process of catalytic oxidation of ammonia and one of the by-products of the process is N2O, which is released into the atmosphere.
Livestock farming is another source of N2O. The gas is produced through the denitrification and nitrification processes of organic nitrogen that is found in the livestock dung and urine. Its production, therefore, depends on the components of the urine or manure, the amount of oxygen, and the type of bacteria found in the manure system. Both the anaerobic and aerobic processes of manure handling can produce N2O.
Domestic sewage also has the potential to produce N2O. The drainage system in homes collects human waste and waste water, which includes sink drain, shower water, effluents from washing machines among others. This mixture is then transported to either a treatment plant or a septic system. Some of the components of the sewage include ammonia, urea and proteins. Through the nitrification process, these compounds form nitrate with nitrate gas as an intermediate product (Stern, et al., 1992).
Another greenhouse gas produced by human activities is methane. The most common source of methane is rice cultivation. Flooded rice cultivation combined with the decomposition of organic matter leads to the formation of methane. Flooded soils contain more organic substrates, moisture, and oxygen-depleted conditions, which are favorable for methane production. However, the amount of methane produced varies with production practices, soil conditions and the climate.
The digestive system of ruminant animals including buffalo, cattle, sheep, and goat produces methane gas through enteric fermentation. The digestive systems of these animals convert plant food into nutritious fiber. In the process methane is produced as a by-product and contributes to global warming. The decay of animal droppings also releases methane. The Environmental Protection Agency in the US asserts that ruminants produce approximately 80 million metric tons every year.
Landfills produce substantial amounts of methane. They are made up of a methane collection system that holds all the methane produced from the decomposition of trash. Half of the gas produced in the landfill is methane while another half is carbon dioxide. An example of a landfill is the North Wake County Landfill located in North Carolina (Maslin, 2007).
Treatment of waste water also produces methane gas. Industrial and municipal sewage is treated to get rid of the suspended solids, soluble organic matter, chemical contaminants and pathogenic organisms. If the waste is treated in the absence of oxygen, methane gas will be produced. The sludge produced in the process could also decompose to produce more methane. Other than direct emissions, burning of soil can lead to the production of methane.
Chlorofluorocarbons are major causes of global warming too. Some of the sources of CFCs include home appliances, such as microwaves, washing machines, air conditioners, and aerosols (Maslin, 2007). In trying to make their lives more comfortable, human beings have embraced the use of these products. In the process, the appliance release CFCs into the atmosphere causing global warming.
To prevent more global warming, human beings should change their activities in many ways. For instance, they should embrace new technologies that use cleaner energies. For instance, using solar power or wind power would prevent the release of CO2 into the atmosphere and cut down on global warming. Similarly, the transport sector should embrace the use of cleaner energies like bio-fuel and electricity (Stern, et al., 1992). This, therefore, calls for the manufacture of electric cars and trains and getting rid of vehicles that use fossil fuel. Meanwhile, adaptation measures, such as using public transport could be very useful in preventing climate change. Use of bicycles and walking are other options that can be embraced.
Green agriculture is also another step that can be used. Farmers can use green houses in the production of crops and stop the use of synthetic fertilizers. Instead of that, they could use manure from animal droppings to improve their production. Additionally, human beings should stop the use of aerosols and other home appliances that contain CFC.
Natural Causes of Global Warming
Those in opposition of the idea that human beings are responsible for global warming also have several genuine evidences to back up their claims. While it might be true that greenhouse gases cause global warming, there are various natural sources of these gases, which are not linked to any human activity. To begin with, carbon dioxide is a natural gas that could be found either in the water or in the air as a part of the carbon cycle. Crowley (2000) alleges that, through the natural respiration process, living things take oxygen and exhale carbon dioxide into the atmosphere: Autotrophic respiration produces about 60 Pg C into the air every day while 55 Pg C comes from heterotrophic respiration. CO2 can also be produced naturally through volcanic eruption.
Similarly, there are a number of natural processes that produce nitrous oxide, which causes global warming, and therefore, it cannot entirely be blamed on human beings. For instance, the microbial activities that occur in the soil produce N2O. Vitousek (1994) argues that all that human beings can do is to accelerate the N2O formation process in the soil through the use of fertilizers.
Methane is also produced by various natural processes. For instance, gas fields and natural geological deposits produce substantial amounts of methane. Decay of organic substances deposited under the earth surface release some methane. The fields of natural gas are rich in deposits of methane that is harvested by drilling of wells. South Pars/Asalouyeh gas field is just but an example of the many gas fields in the world (Vitousek, 1994). Furthermore, the main component of natural gas is methane.
Wild fires also produce methane gas. It is estimated that they release up to 5 Tg of methane every year. This mainly occurs because of incomplete combustion of the biomass. Vitousek (1994) alleges that geologic emissions also produce about 64Tg of methane every year. However, he indicates that it is not easy to quantify geologic emissions, because there are various small point sources across the world. The main geologic source is mud volcanoes. Most of them are small, but the biggest could have a diameter of up to 10 kilometers. They often form the boundaries of tectonic plates and in deposits of fossil fuel. More than 1000 mud volcanoes are found in shallow waters and on the land. They release methane, carbon dioxide, helium and nitrogen from within the earth.
Looking at various incidences of climate variation that have taken place over time could also help in determining the natural causes of global warming. Based on a longer time scale, the world has experienced at least four cold and long periods (Crowley, 2000). The warm period recorded about 10o C warmer than the current temperature. Major ice ages were experienced between the warm periods. They are believed to be as a result of continental drift that affects the distribution of heat and ocean currents. The glacial periods have also been witnessed in the current Ice Age. These changes correlate with Milankovitch Cycles, which are linked to the rotation and tilting of the earth on its orbit. As a result, longer snow periods are experienced thus increasing the reflectivity.
Vitousek (1994) also argues that changes in CO2 cannot be the cause of temperature rise, because the temperature changes first before any change in CO2. Since carbon dioxide’s solubility in water and temperature rise is inversely related, it stands that it is the temperature that controls CO2. This is the reason why the ocean releases CO2, when it warns and absorbs it when it cools. Solar variation could also lead to temperature rise. Increased solar activities lead to a deflection of cosmic rays by the solar wind. Cloud formation in low-altitudes decreases and permits more sun rays to strike the earth leading to global warming. Based on the above explanation it could be argued that natural activities have caused the current global warming. Consequently, there is nothing that can be done by human beings to stop global warming.
In spite of the opposing views on the causes of global warming, it is clear that everyone agrees that global warming is taking place and it is mainly manifested through a rise in temperature. The earth is said to have warmed by 1 degree Fahrenheit for the past 100 years. The green house gases that are said to cause global warming include water vapor, CO2, N2O, methane, and CFCs. Those who support the idea of human beings contribute to global warming advocate for the reduction of the release of the gases into the atmosphere. On the other hand, those in opposition argue that human beings can do nothing to stop the warming.