Honors Chemistry 114

Dr. Harry Hecht

April 23, 1997
 

    Growing up as a child, I was very interested in the environment and the outdoors.  It
was not until I entered fifth grade when I learned from an article in a publication called
The Weekly Reader that the process of global warming existed.  Five years passed until I
reached Environmental Chemistry in high school and I learned that both global warming
and the greenhouse effect may become potential problems in the immediate and extended
future.  The intent of the following report is to study the issues concerning global
warming and the greenhouse effect by presenting both sides of the argument in an
accurate and fair manner.  To introduce and discuss this controversial topic in a fair and
understandable manner, graphics, tables, and interviews will be presented to give the
reader a true scientific approach in concluding the legitimacy of global warming.

     The words Global Warming and The Greenhouse Effect are many times used
interchangeably, but the two words differ greatly in meaning.  Global Warming is the
process by which the Earth's annual average temperature increases by a significant
amount over a relatively extended period of time (Newton 154).  The Greenhouse Effect,
on the other hand, is the term used to describe the effect on the Earth's temperature that
results from the capture of heat by molecules of carbon dioxide, water vapor, and other
gases in the Earth's atmosphere (Newton 154).

     The greenhouse effect is a naturally occurring process that allows the earth to heat so
that human habitation is possible.  Figure 1 below describes the processes of the
greenhouse effect.

 

    The atmosphere of the earth contains many gases, but there are only three main gases that make up
the bulk of the earth's air. They include: nitrogen, oxygen, and argon. There are many trace gases that
are found in very minuscule concentrations. Figure 2 and Table 1 below describe the concentration of
the main gases found in today's atmosphere (Brown, LeMay, and Bursten 663).

     Recently, two scientists at the University of California, San Diego, reported that the release of N₂O during the manufacture of nylon may account for nearly 10% of the total increase of N₂O (Benarde 85). The two scientists decided to prove their theory by simulating the industrial production of nylon in the lab. They discovered that N₂O was a significant by-product in the production of adipic acid, the acid that forms the nylon polymer. Benarde also stresses that N₂O may reside in the atmosphere for nearly 150 years after it is produced (Benarde 85). Scientists, such as author Dean Abrahamson who wrote The Challenge of Global Warming, fear that increased concentrations of N₂O may lead to further destruction of the earth's ozone layer. As displayed below, nitrous oxide reacts with oxygen in a two step process to form nitrogen oxides, which react furthermore with ozone to produce molecular oxygen and nitrogen dioxide (Abrahamson 253).

(1) N₂O + O  2NO

(2) NO + O₃  NO₂ + O₂

Figure 3 below displays the raising concentrations of nitrous oxide.

     Methane is also produced in considerate amounts by the action of termites. Termites act as cattle and release methane as they digest food. Many scientists believe that the destruction of the rain forests may be the reason for the increase in global methane concentrations. They believe that as more forests are cut down, dead trees may become attacked by termites, further increasing methane concentrations (Newton 10). It has been shown that methane is the most rapidly increasing greenhouse gas. Nevertheless, the source of increasing methane concentrations and its long-term effect on climate is still largely unknown (Newton 10).

(1) CF₂Cl₂(g) + hv  CF₂Cl(g) + Cl(g)

(2) Cl(g) + O₃(g)  ClO(g) + O₂(g)

(3) 2ClO(g)  O₂(g) + 2Cl(g)

(4) 2O₃(g)  3O₂(g) *Chlorine catalyst

     It is starting to be understood that CFCs may play an important role in the greenhouse effect. CFCs have the tendency to absorb a band of radiation that is not absorbed by any other gas in the atmosphere. This band of radiation that is absorbed by the CFCs normally would escape from the atmosphere through the atmospheric window, a term referring to the hole created in the atmosphere due to the absence of band absorbing gases (Newton 11).

     CFC's ability to destroy the ozone layer prompted the United States government to become involved. The 1990 Clean Air Act stated that CFC production in the United States must terminate by the year 2000. President George Bush later learned in 1992 that stratospheric ozone depletion was increasing, which forced Bush to move the deadline to 1995 (Brown, LeMay, Bursten 670).

     Today, scientists are beginning to see a declining trend in the concentration of CFC-11 and CFC-12 in the upper atmosphere. Nevertheless, scientists still contend that CFCs will still play major roles in the greenhouse effect and ozone depletion because of their lifetimes. CFC-11 and CFC-12 have atmospheric lifetimes of 65 and 130 years, respectively (Evans 89). Some rarer chlorofluorocarbons, such as CFC-115 have average lifetimes of 400 years (Evans 88). Figure 5 below describes the concentrations of the CFC-11 and CFC-12, the most used chlorofluorocarbons. One may note from Figure 5 that the concentrations of both CFC-11 and CFC- 12 rise exponentially during the 1980s, but begin to level off slightly in the 1990s when CFCs became banned.

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     Carbon dioxide is a colorless gas with a faint, pungent odor and an acidic taste. Carbon dioxide is an essential plant nutrient and has an important determination of the earth's thermal balance. Most controversy over CO₂ in today's world revolves around the question of how and to what extent is CO₂ formed. According to Dean Abrahamson in his book The Challenge of Global Warming, levels of CO₂ began to rise during the industrial revolution when coal, oil and natural gas were burned. Abrahamson contends that human activities are currently prompting nearly 7 billion tons of carbon to be released into the atmosphere. Moreover, Abrahamson alleges that nearly 6 billion tons of carbon dioxide a year are liberated by fossil fuel combustion alone (Abrahamson 7).

     To put this allegation into perspective, consider the following data that has been developed to determine approximately how much CO₂ a clean burning car may emit. The following equation describes the combustion of the organic alkane, octane (C₈H₁₈). For this experiment, we are going to call octane our gasoline, even though gasoline is a mixture of many different kinds of volatile hydrocarbons containing varying amounts of aromatic hydrocarbons. Therefore, combustion of gasoline (C₈H₁₈) yields:

2C₈H₁₈ + 25O₂  16CO₂ + 18H₂O

By observing the preceding equation, one can see that the molar ratios of octane to CO₂ is somewhat high, a 2:16 ratio. Because water has a density of 1.0 g/cm³ (g/mL) and gasoline is observed to float on water forming a heterogeneous mixture, one may approximate the density of gasoline to be approximately 0.8 g/cm³. Therefore, assume that one combusts 1 milliliter of octane, which would equal 0.8 grams of octane. Using simple stoichiometry:

This calculation provides us with an answer of 0.056 moles of CO₂ or 2.46 grams of CO₂, or approximately 1.26 liters of CO₂ at STP (1 atmosphere pressure and 273 K).  Chemists are currently searching to find alternative fuels that, when combusted, would have low fuel to carbon dioxide molar ratios. One such fuel that has gained much support throughout the last 5 years is ethanol. Ethanol is produced through a simple fermentation process and can be produced with high efficiency. The following equation describes the combustion of ethanol:

CH₃CH₂OH + 3O₂   2CO₂ + 3H₂O

As one can see, the molar ratios between the fuel, ethanol, and CO₂ is a much lower 1:2 ratio. Indeed, ethanol is becoming more widely used as an economical fuel that has a much "friendlier" affect on the atmosphere.

     Scientists have proposed many other theories to explain why carbon dioxide levels have been rising. One of these theories deals with the destruction of the earth's forests. The following equation describes the process of photosynthesis, the process utilized by plants and some microorganisms that generates ATP from energy captured by light.

6CO₂ (g) + 6H₂O (l)  C₆H₁₂O₆ (aq) + 6O₂ (g)

As displayed in the preceding equation, CO₂ is a reactant in the process of photosynthesis. Therefore, many scientists believe that as more forests are cut down, the process of photosynthesis will not occur as rapidly, resulting in an increased amount of global CO₂ greenhouse gas. Ecologist George Woodell believes that "...rapid deforestation in the tropics is resulting in a surge in the release of carbon (in the form of CO₂) from forests into the atmosphere. Current estimates are that the net release from deforestation globally is 1 to 3 billion tons of CO₂ annually" (Abrahamson 74-76). Woodell further states that the total content of CO₂ in the atmosphere is in the excess of 700 billion tons and the annual absorption of CO₂ by plants globally through photosynthesis is about 100 billion tons, nearly one-seventh of atmospheric CO₂. Therefore, Woodell believes that the CO₂ crisis in the world may be repaired by mass reforestation of nearly 2 million square kilometers until the atmospheric CO₂ level reaches equilibrium (Abrahamson 81).

     Meanwhile, industry has been shown to play a crucial role in the particulates and pollutants that are able to enter the atmosphere. It has been proven throughout the years that industrial sulfur emissions play a role in the development of acid rain, which has detrimental consequences. Nevertheless, some environmentalists assert that industries must become more "environmentally friendly" by installing scrubbers on smokestacks. Author Dean Abrahamson estimates that installing scrubbers in large fossil fuel burning facilities such as electric power plants may reduce the annual CO₂ production of the United States by up to 30% (Abrahamson 25). The implementation of CO₂ scrubbers would further benefit the environment because the recovery of more than 99% of sulfur contained in coal is required prior to CO₂ scrubbing (Snyder).

     There remains one more source of CO₂, a source that is controlled only by nature. Volcano eruptions have tremendous effects on our temperatures, weather patterns, and perhaps carbon dioxide levels. It has been known throughout history that volcanic activities cool the earth. One of the first to really document this phenomena was Benjamin Franklin. The year was 1784 and Franklin observed that much of the northern hemisphere in the summer of 1783 was inundated in a dry, summer fog that was not easily dissipated by the sun's rays. Franklin wrote in his daily journal:

     It was later discovered that the winter temperatures in Philadelphia were nearly 5 degrees Celsius below the long-term winter average. Franklin was correct in speculating that volcanic activity, specifically that of the Laki eruption in Iceland, was responsible for producing the "smoke" and the abnormal weather patterns (Blong 64).

     The world has experienced similar cases to that of Franklin with the eruption of Mount St. Helens in 1980 and the recent 1991 Mount Pinatubo eruption. According to Lin Sutherland, author of The Volcanic Earth, Mt. ETNA is the premier greenhouse volcano because in one year's time, the volcano contributes well over 25 million tons of CO₂ into the atmosphere (Sutherland 51).

     The stories of CO₂ production by volcanoes, both active and inactive, is fascinating. Consider the following dialogue written by one resident who lived near the erupting volcano Vesuvius (Italy) in 1906.

Gases and aerosols have also been responsible for the large number of animal deaths. Prior to the eruption of Mount Pelee in 1902, the sulfur fumes were so potent that horses dropped dead throughout the streets of St. Pierre. An appropriately named landmark in Yellowstone National Park, Death Gulch, was the home to the 1897 killing of hares, squirrels, and eight bears. Later studies concluded that the accumulation of CO₂ and H₂S were the culprits in the killing of the animals (Blong 329).

     Author Lin Sutherland contends that with all the volcanoes throughout the world, their yearly contribution of CO₂ to the atmosphere ranges from 130-175 million tons of CO₂. (Sutherland 51). To conclude the discussion of carbon dioxide, refer to Figures 6 and 7 below which describe the atmospheric concentration of CO₂.

     Some scientists, nonetheless, contend that they may be observing patterns throughout the earth's weather phenomena that may link global warming to the flooding that has plagued the midwestern states of South Dakota, North Dakota, and Minnesota throughout the spring of 1997. According to the April 8, 1997 airing of NBC Nightly News with Tom Brokaw, scientists are observing cyclical patterns throughout the atmosphere that exhibit both natural and unnatural characteristics. NASA scientist Anthony Deljegico claims that 1995 was the hottest year on record and that 1996 was not far behind. Nevertheless, Deljegico says "There is little doubt anymore that the earth has gotten significantly warmer over the 20th century." (NBC News).

     New research obtained by Kevin Trendberg from the National Center of Atmospheric Research (NCAR) shows a steady increase in the evaporated moisture from both sea and land, specifically the U.S. subtropics and the Atlantic and Pacific gulfs. Trendberg speculates that "Moisture has increased by about 10 percent over the last 20 years or so." The question that remains to be answered is whether or not global warming is having a significant effect on our climate to prompt heavy rainfall and snowfall amounts. Deljegico and Trendberg both concluded in their interviews that they are not yet blaming global warming for the flooding, but that they hope further studies in the years to come can help to answer the questions that scientists are pondering today (NBC News).

     With the facts in hand, one may ask how the temperature fluctuations throughout the years have prompted scientists to conceive such a theory like global warming. To aid in answering this question, refer to Figure 8 below.

     Figure 9 below describes the temperature anomalies with a specific emphasis on those years and preceding years when volcanoes erupted. For example, consider the 1991 eruption of Mount Pinatubo, located in the Philippines. Figure 9 describes the somewhat dramatic drop of the temperature in 1992 compared to that of the preceding years. Also, note the drop in the temperature in the years following the eruption of the Agung, a volcano located near Bali, which killed 1,148 people in 1963 (Blong 98).

* One of the most common and perhaps feared predictions of global warming is the rise of the sea levels. Scientists predict that if the global temperature was to rise by 1.5 degrees Celsius, this change in temperature would result in melting of the polar ice caps and glaciers. As a result, shorelines throughout the world would change and some islands would become nonexistent (Newton 81).

* Global warming may have both beneficial and harmful effects on plant life throughout the earth. For example, consider the following potential effects on agricultural commodities: (1) A reduction or increase of average yields of corn, soybeans, and wheat. Increased yields would most likely occur in the northern latitudes where warmer conditions would provide longer growing seasons. Decreased yields may occur in the mid-latitudes where high temperatures may shorten the crop's life. (2) An increase of corn, soybean, and wheat products would result due to increased CO₂, which may increase a plant's growth. (3) The flooding of near-coastal agricultural lands may result due to a dramatic sea level rise.

* According to Biologist Robert L. Peters, "If the planet warms as projected, natural ecosystems would be stressed by large changes in temperature, moisture patterns, evaporation rates, and other associated chemical and physical changes. For example, we know that one race of the dwarf birch, Betula nana, can only grow where the temperature never exceeds 22 degrees Celsius, then we can hypothesize that it would disappear from those areas where global warming causes temperatures to exceed 22 degrees Celsius. We also know from the fossil record that some species have become completely extinct because they were unable to find suitable habitat when climate change made their old home unlivable...Finally, not all the changes for wild systems would be negative. Some species would expand their ranges and have greater abundance. However, the most optimistic thing that should be said about the future of natural systems under a regime of warming climate is that a great deal of rearrangement would occur, and it is most likely the outcome will be widespread extinction of species." (Abrahamson 82)

* Finally, authors Joel Smith and Dennis Tirpak contend that global warming may have significant impacts on human societies, particularly on human health. For example, Smith and Tirpak estimate that global warming may produce a net increase in deaths due to growth in respiratory, cardiovascular, and cerebrovascular diseases. They also write that diseases that are carried by ticks, fleas, and mosquitoes may increase in certain regions (Smith and Tirpak 525-526).

     If global warming was to occur, it is obvious that the world would change, but would the change be all that bad? This is the same question that Meteorologist Dan Carlson asks himself when he ponders the idea of global warming. Carlson explained in his interview that even though flooding of low lying coastal areas would be inevitable, global warming would extend the summer and provide a longer growing season. Agricultural areas such as South Dakota and even parts of Canada may be greatly benefited by a change in climate that would accommodate a more favorable climate for crop production.

     It has became apparent to this author that the issue of global warming is one of extreme controversy due to the recent awareness of the potential problem. Throughout this research study, I encountered many sources that seemed to exaggerate the problem at hand. For example, some sources that I encountered painted an errie outlook to the future if global warming was to occur. It is obvious that the world would be changed dramatically if such a process was to happen, but our world today changes at a remarkable rate. For example, scientists estimate that the continents today are moving at a rate of about 1 inch per year (Grolier Encyclopedia). I also believe that there are other issues today that require much more of our attention. During my interview with Meteorologist Dan Carlson, Carlson expressed his opinion that we must look into other environmental and global issues that are affecting our world today. For example, Carlson expressed his concern for the issue of acid rain. Acid rain is becoming a problem in our world today because the acidic rain has the capabilities to destroy forests, natural buffered lakes, and may also affect human and aquatic life.

     I believe that the issue of global warming should be addressed and that everybody should learn about it. I do believe, however, that the issue at hand is not as legitimate as some scientists believe. I base my opinion on the insufficient amount of data that has been retrieved supporting the theory. It is obvious by the graphs presented throughout the report that many of the greenhouse gases are increasing and that our temperature does seem to fluctuate. Nevertheless, one must observe these graphs and note the up-and- down trends that show such an oscillation throughout history.

     In conclusion, I believe we must continue to monitor the changes in our atmosphere and look to alternative sources of fuel, such as ethanol (as described above), to preserve our planet for the years to come. If global warming does occur, we must adapt to the coming changes so that we can continue to prosper as a world-wide society.