Anthropogenic and Natural Causes of Global Warming - Essay Example

? Anthropogenic and Natural Causes of Global Warming GSC125 Weather and Climate Term Paper The paper discusses the various causes of global warming, which are classified into two: anthropogenic or caused by man, and natural. For the anthropogenic causes, the greenhouse gases are presented while underlining CO2 as the one that occurs the most. Other greenhouse gases include CFCs, methane and nitrous oxide. On the other hand, the natural causes include solar changes or solar radiation, volcanic eruptions and clouds. There are, however, issues surrounding the significance of CO2 over non-CO2 gases and solar radiation. Moreover, there are also issues concerning whether the natural causes outweigh the anthropogenic causes. Introduction Global warming is defined as the result of the accumulation of CO2 and other emissions that trap heat in the atmosphere (“Global Warming,” UCSUSA 2010). Moreover, it is considered as “the worst and most complicated issue” that world leaders have to deal with nowadays (“Global Warming,” NYTimes 2011). Basically, global warming affects all people on earth, especially those in areas with extreme air pollution (“The Hidden Cost,” UCSUSA 2010). Global warming also further affects the human race through increase in the occurrence of infectious diseases because those microorganisms that thrive only in high temperatures are supported by the increasing heat (Trimarchi 2012). According to Trimarchi (2012), this and the other calamities that global warming brings with it will further lead to various other negative effects like famine, war and starvation. Global warming will also affect the environment itself through the occurrence of various storms and hurricanes, extreme drought in some parts of the world while abnormally increased precipitation in others, heat waves, melting of the polar ice caps, rise in sea levels and the eventual destruction of the tundra and freshwater ecosystems (Trimarchi 2012).Such effects will not only destroy ecosystems but will also eventually cause a series of events that ultimately leads to chaos in and destruction of the human society. Based on a report by the U.S. National Research Council in 2006, “The Earth is the hottest it has been in at least 400 years” (“Global Warming,” Stanford 2008). Furthermore, according to the same report, the latest global temperature increase of 0.3°C to 0.6°C is in fact the “largest” increase in surface temperature in 1,000 years (“Global Warming,” Stanford 2008). The main culprit behind this, according to most scientists and publications, is greenhouse gases. The greenhouse gases that cause global warming include carbon dioxide, methane, nitrous oxide, chlorofluorocarbons, but among these, carbon dioxide has the most volume in the atmosphere at 55%, and is therefore regarded as the main cause of anthropogenic or man-made global warming (Ganesh 2011). There is, however, the question of what is the exact cause of global warming and how much of it is brought about by nature and how much is caused by man. Does present research and scientific literature shed light on these issues or do we need further research on them? In order to remedy the situation and prevent its dire effects, there is therefore undoubtedly a great need to know the exact causes of global warming as well as how many of them is contributed by man and how much by nature. There is also a need to know the issues surrounding these causes. Literature Reviews The Anthropogenic Carbon Dioxide (CO2) Factor One of the causes of global warming is the release of carbon dioxide, or CO2, especially from the industrial processes involved in the burning of fossil fuels (“Global Warming,” Geowise.com, 2006). Among these fossil fuels, coal, which is increasingly being used in the United States and China, contributes the greatest percentage of CO2 to the atmosphere because of potentially large emissions compared to oil or natural gas (Hansen et al. 2000). CO2 has a long shelf-life that makes it stay in the air for the next 500 years, and with a concentration of 355 ppm in 1990 and an increasing rate of 1.5 ppm every year (Ganesh 2011). However, CO2 is produced not only by fossil fuels but also by other human activities and even natural phenomena. Nevertheless, fossil fuel use seems to be a pressing issue. According to Nordell (2003), before the advent of fossil fuel use, the only net heat source on Earth was the “geothermal heat flow,” but everything began to change when the use of nonrenewable energy sources started and CO2 began to dissipate into the atmosphere. Another thing is that, according to Ganesh (2011) and based on the 2007 report of the United Nations Intergovernmental Panel on Climate Change, or IPCC, CO2 contributes about 55% to global warming and that industrial countries, especially those that use mainly fossil fuels, constitute around 76% of the total dissipated CO2. Goel and Bhatt (2012), however, in a very recently published review article for the International Journal of Life Sciences Biotechnology and Pharma Research, states that CO2 contributes to greenhouse effect not 55% but only 50%. Moreover, the reason why it was previously mentioned that fossil fuel is a major issue when it comes to the production of CO2 is that the larger portion of dissipated CO2 – 67% – comes from fossil fuels, while the remaining 33% comes from other human activities such as deforestation, land clearing and combustion, or anything else that involves the use of fire (Ganesh 2011). Carbon dioxide does not absorb the sun’s light energy. Instead it absorbs the heat energy from the earth and when it does, the CO2 molecule goes into an “excited unstable state” (“How does carbon,” Michigan State University 1994). It will then attain its stability only if it releases the heat energy it has absorbed. The problem is that some of this heat energy is not let out into space and will therefore go back to earth. Meanwhile, CO2 simply allows the light energy from the sun to enter the Earth’s atmosphere, which means that CO2 does not prevent this light energy from getting in. Carbon dioxide molecules are known to have a “special ability to absorb and reradiate the sun’s longer wavelength radiation” (Paterson 2011). This consequently leads to the warming of the troposphere and the increase in “high-altitude or cirrus cloud” that further amplify the warming process (Paterson 2011). This means that as the sun’s light energy hits CO2 molecules, the CO2 molecules simply absorb then radiate back the light. The usual problem with the process, however, is that not all of the reradiated light is reflected back into space and the rest naturally stay on Earth and consequently contribute to global warming. Carbon dioxide, however, does not only come from the burning of fossil fuels. All of atmospheric CO2 must not have come from human use alone. Some of them came from natural phenomena such as solar changes, atmosphere-ocean interaction and greenhouse gases that are already in the atmosphere (Paterson 2011). The solar changes may include irradiance and magnetic field effects, while the atmosphere-ocean interaction may include climatic oscillations and unforced internal variability (Paterson 2011). Controversies Involving the Role of CO2 in Global Warming Despite all the aforementioned evidence on the seriousness of the global warming situation and the obviously big role that CO2 plays in its occurrence, recent data reveal that CO2 is not the main factor involved in global warming. In fact, according to Paterson (2011), in his recently published commentary for Geoscience Canada, the fact that CO2 emission is actually the main cause of concern when it comes to global warming is being debated as of the moment. Although the media has been creating the hype about the seriousness of anthropogenic causes of CO2, it remains that “no satisfactory explanation” can ever justify that 0.04% of CO2 in the atmosphere is indeed an alarming cause of global warming (Paterson 2011). How exactly can scientists determine that CO2 is indeed the one responsible for trapping heat when it accounts for only a very small percentage of the elements in the atmosphere? Besides, even if CO2 were really the culprit, then it would still certainly take a lot of explanation how a mere 0.04% can absorb large amounts of heat. Moreover, based on past geologic records, “Past temperature increases have always preceded, not followed, increases in CO2” (Patterson 2011). This means that global warming could potentially be the ultimate cause of the production of CO2, and if CO2 causes further global warming then a vicious circle is being presented here. The proof that global warming may be the cause of the increase in atmospheric CO2 is that for the past 400,000 years, temperature rose first before the concentration of CO2 increased (Patterson 2011). This hypothesis is, however, still being studied further. One probable explanation for this is that “solar warming, over a long period of time, causes the oceans to outgas CO2 [and] cooling results in more CO2 entering solution” (Patterson 2011). This solar warming may be synonymous or exactly the same as the phenomenon of solar irradiance (Lean & Rind 1998). Another point made by Patterson (2011) in his commentary is that “there is no correlation between CO2 and temperature.” Past records of CO2 concentration show that despite high levels of CO2 earlier in history, the temperature was several degrees lower. This means that one cannot establish a clear and definite pattern which is based on the idea that an increase in CO2 causes a corresponding increase in temperature, which translates as global warming. The problem is that the independent and dependent variables are unknown. There is still a controversy where one is confused whether CO2 is dependent on temperature or the other way around, or vice-versa. Nevertheless, whether it is CO2 that causes an increase in the temperature, or the temperature that makes CO2 levels rise, the fact remains that there is still global warming – unless temperatures actually consistently rise every year. This is, however, not the case. Patterson (2011) points out that one of the “serious mistakes in analysis” made by scientists about predicting temperature and global warming patterns of the Earth is that “the 20th century is likely the warmest century” simply because “the 1990s was the warmest decade, with 1998 as the warmest year in the last 1000 years.” This conclusion, which is also known as the “Hockey Stick Curve,” was the one adopted by IPCC, which reported a “steady increase in global temperature” (Patterson 2011). More recent information, however, postulates that “the 20th century is [actually] not exceptionally warm when compared with that of the 15th century,” and that the mean temperature of the Earth has been “roughly level globally” since 2002 (Patterson 2011). This means that the IPCC was based either on a pure mistake or a poorly investigated phenomenon. The question that remains, therefore, is whether CO2 still counts as a viable factor in causing global warming or is it already being replaced by a more serious factor? The fact that global warming exists presupposes the presence of a cause, whether or not it is CO2. The Non-Carbon Dioxide Factor According to Hansen et al. (2000), it is not CO2 that has been responsible for the rapid warming of the recent decades but mainly “non-CO2 greenhouse gases, or GHGs, such as chlorofluorocarbons, CH4, and N2O,” which are all not by-products of fossil fuel burning. These non-CO2 greenhouse gases have molecules that, like CO2, also absorb and release heat energy from the Earth and reflects some of it back to Earth, while allowing all of the sun’s energy to simply penetrate the atmosphere. Chlorofluorocarbons, or CFCs, make up 24% of the greenhouse gases (Ganesh 2011). CFCs usually come from “leaking air conditioners and refrigerators, evaporation of industrial solvents, production of plastic foams, aerosols, propellants” and many others (Ganesh 2011). The damage that CFCs cause may not be as much as CO2 considering the amount of the former in the atmosphere, which is 55%, but CFCs certainly, together with nitrous oxide, cause the depletion of the ozone layer in the stratosphere and that CFC molecules can trap “1500 to 1700 times more heat…than CO2” (Ganesh 2011). The lifetime of CFCs, which is 65 to 110 years, and its increasing rate of 0.5% annually both contribute to the prolonged global warming that the Earth experiences (Ganesh 2011). Furthermore, Hansen et al. (2000) considers CFCs, particularly man-made aerosols, as the “largest source of uncertainty about future climate change.” Methane, or CH4, primarily comes from the “microbial decay of organic matter under anoxic conditions [as well as] domestic ruminants,” or specifically, from the digestive tracts of grazing animals like cattle (Hansen et al. 2000; Ganesh 2011). However, it is a fact that “anthropogenic sources [of CH4]…may be “twice as great” as the natural source” (Hansen et al. 2000). This means that activities such as “rice cultivation, bacterial decay in landfills and sewage, leakage during mining of fossil fuels, leakage from natural gas pipelines, and biomass burning” all contribute to the increase of the amount of CH4 in the atmosphere (Hansen et al. 2000). Methane may also come from sheep, termites, natural wetlands, swamps and landfills (Ganesh 2011). This means that several activities indeed bring about the production of CH4 and that includes not only agricultural but also urban activities. Nevertheless, according to the IPCC, CH4 constitutes only a mere 18% of the greenhouse gases (Ganesh 2011). However, just because it accounts for only 18% does not necessarily imply that the CH4 molecule can trap less heat than CO2 molecules, which account for 55% of the greenhouse gas composition. Considering that CH4 is “20-30 times” more efficient than CO2 in terms of trapping heat, the mere 18% of CH4 in the atmosphere may likely trap more heat than the 55% of CO2 (Goel & Bhatt 2012). Methane’s life span, which is around 7 to 10 years, plus its increasing rate of 1% per year somehow make it as equally alarming as CO2 and CFCs (Ganesh 2011). Another non-carbon chemical that allegedly helps cause global warming is nitrous oxide, or N2O. Nitrous oxide accounts for around 6% of greenhouse gases and causes both the trapping of heat in the troposphere and the depletion of the ozone layer in the stratosphere (Ganesh 2011). Nitrous oxide usually comes from nylon products, burning of biomass and nitrogen fuels like coal, and breakdown of nitrogen fertilizers, wastes coming from livestock, and groundwater contaminated with nitrate (Ganesh 2011). With a life span of 140 to 190 years and with the capacity to trap heat 230 times as CO2 despite the mere 0.2% of annual increase, N2O is also an important factor in the phenomenon of global warming (Ganesh 2011). Both the anthropogenic and the natural factors actually make up the UHI or Urban Heat Island that is caused by pollution and the combined human activities in the urban areas such as household heating, car use and industrial processes (Goel & Bhatt 2012). The Natural Factors One of the natural factors that contribute to global warming is solar changes. These solar changes may include irradiance and magnetic field effects, while the atmosphere-ocean interaction may include climatic oscillations and unforced internal variability (Paterson 2011). According to Lean and Rind (1998), although not yet fully understood, radiation from the sun somehow leads to a “radiative forcing” response of the Earth’s climate system. This means that the sun’s heat may itself be responsible for the occurrence of global warming, although the mechanism behind this is still not fully known and even its certainty is questionable. However, a recent commentary of Patterson (2011) states that solar radiation produces a “thermal energy flux” that combines with the solar magnetic field in order to “shield against cosmic rays” and eventually cause global warming. The cosmic rays that the thermal energy flux of the sun shields against comes from outer space and these cosmic rays “cause clouds to form in the troposphere” and these clouds bring about a cooling effect (Patterson 2011). If, therefore, there is no thermal energy flux to shield the cosmic rays, then clouds in the troposphere will be continually formed, thus consequently cooling the atmosphere. This is, however, possible only if there were no sun. In fact, Rao (2011) stated that these “primary galactic cosmic rays” generate “low-level cloud condensation nuclei” and these nuclei are mainly responsible for reflecting solar energy back into space and thus making the Earth cool. Aside from solar changes, volcanic eruptions can also the production of large amounts of CO2, like Mount Etna in Sicily, which is known to add as much as 25 million tons of CO2 to the atmosphere every year (Goel and Bhatt 2012). Clouds are also among the natural elements that contribute to global warming by acting as “main absorbers of infrared in the atmosphere” (Nordell 2003). Infrared rays of light are natural sources of heat and, when absorbed, are therefore expected to produce heat that could eventually contribute to the warming of the Earth. Although not thoroughly explained, according to Nordell (2003), this leads to the conclusion that although all greenhouse gases were eliminated, the Earth would still experience “98% of the current greenhouse effect,” thus implying that greenhouse gases account for very little of the current global warming state. This statement somehow complements that of Goel and Bhatt (2012) when they stated that even if nothing is done in order to minimize the production of greenhouse gases, “the world will only see a global temperature increase of about 1°C in the next 50-100 years.” This statement further implies that greenhouse gases caused by human activities actually have very little, if not an insignificant, role in the occurrence of global warming. Discussions The controversies surrounding the role of CO2 in global warming, as presented by Patterson (2011), are indeed thought-provoking. These controversies, when presented vis-a-vis information about the effects of solar irradiation and the role of other gases, somehow bring about new insights or perhaps old ones. First of all, Patterson’s claim that there is only 0.04% of CO2 in the atmosphere and that this cannot guarantee a definite role in global warming somehow underlines the principle that what is little may not have a big effect. Indeed, this is logical, although it fails to consider certain other factors like the efficiency of CO2 in trapping heat, and its life span. Patterson may still be partially wrong in stating this claim regarding the inability of a mere 0.04% CO2 to help cause global warming simply because he has not considered the fact that the life span of CO2 is around 500 years (Ganesh 2011). Therefore, what may be caused by what is 20% in the atmosphere for 50 years may even be surpassed by what may be caused by 0.04% of CO2 in the atmosphere for 500 years. Patterson’s (2011) second claim – that “past temperature increases have always preceded, not followed, increases in CO2” – may actually be true, and it may be logically correct that global warming may be the one responsible for the production of CO2 and everything may simply be a vicious circle. Nevertheless, what should have been investigated by Patterson was the original cause of the rise in temperature or the first cause of the increase in the amount of CO2. If what he has observed is a series of increases in temperature and subsequent increases in CO2, then how could he be sure which part of the series is the cause and which one is the effect? Certainly, the proximity of two events cannot be regarded as a guarantee that the first one is the cause and the second one is the effect. This claim may therefore have several weaknesses. Patterson (2011) then silently rejects this claim when he said in the end that “there is no correlation between CO2 and temperature.” Nevertheless, a non-CO2 factor may have a correlation with temperature. Patterson’s further claim that the prediction of increasing global warming in the 20th century may be the only one that is sensible simply because past data do not support the conclusion. This, however, must be investigated further since there is also a possibility that the amount of CO2 in the atmosphere may indeed have NO bearing on the increase in temperature, and perhaps a non-CO2 factor may be involved. However, if the claims of Patterson regarding the insignificance of CO2 in the occurrence of global warming are true, then perhaps there is more credibility to the theory of Hansen et al. (2000) that it is the non-CO2 greenhouse gases that are more responsible for global warming. Moreover, it is also possible that Lean and Rind (1998) may be right in their theory that it is the sun itself that has been causing this global warming phenomenon. Hansen et al. (2000) theorized that the non-CO2 greenhouse gases are more responsible for global warming compared with CO2. Based on the aforementioned data on CO2 and the three non-CO2 greenhouse gases from Ganesh (2011), the following table can be conceived: PERCENTAGE LIFE SPAN EFFICIENCY IN TRAPPING HEAT ANNUAL INCREASE RATE CO2 50-55% 500 years X 1 1.5 ppm CFCs 24% 65-110 years X 1500-1700 0.5% CH4 18% 7-10 years X 20-30 1% N2O 6% 140-190 years X 230 0.2% From the data above, one can conclude that, if all factors were considered equal and bearing the same weight as each other, it is CFCs that are mainly responsible for global warming among the anthropogenic causes. Despite the fact that CO2 exceeds it by around 30% in matters of percentage, it is not far behind when it comes to life span and it is definitely much higher when it comes to trapping heat. The value of “X1500-1700” cannot be compared with those of CO2, CH4 and N2O, which seem negligible when compared with such magnitude. What follows CFCs is N2O but the percentage of N2O molecules in the atmosphere might be so low that its can reduce their overall aggregate effect. Nevertheless, these deductions are merely hypothetical as one needs to know the individual specific implications of each of the criteria before making conclusions as to which particular molecule contributes the most to global warming. Aside from the idea of on which particular element global warming mostly depends, another issue regarding the causes of global warming is whether the anthropogenic causes are really not as significant as the natural causes. Nordell (2003), as well as Goel and Bhatt (2012), all imply in their statements that global warming is mostly caused by natural factors and that removing the anthropogenic factor would simply amount to nothing. This is, however, opposed by Huber and Knutti (2011), who theorized that “solar forcing contributed only about 0.07°C to the warming since 1950” and that it is indeed “individual contributions [that are responsible for the] observed temperature of about 0.55°C since the 1950s,” thus implying that the human factor was in fact responsible for global warming and not the sun. Conclusions Although global warming is real, there is a need to pinpoint its cause for the purpose of putting an end to it. Its causes, however, are not only several but also surrounded by several issues, but still one gets a lot of insights from the controversies and opposing arguments. The first issue is whether it is really CO2 that is the main cause of global warming, or the non-CO2 greenhouse gases or solar radiation. Although theories point out to non-greenhouse gases and solar radiation, still CO2 may not be totally neglected or labeled as insignificant considering the huge amounts of coal, oil and natural gas burned everyday. Further investigation is therefore the key and this must answer the question, “What exactly is the main cause of global warming and how significant is it compared to other causes?” The second issue regarding the causes of global warming is whether it is true that the effects of the natural causes outweigh those of the anthropogenic causes. Although there are also varying claims to both sides, further research and investigation is necessary. The point of further research is to objectively determine first what factors are responsible for global warming, and after ascertaining these factors then one should try to find out how much of each is contributed by nature and how much by man. Furthermore, finding out how much is contributed by each of the two factors is not enough. One should also try to determine if the percentages of contributed CO2 or non-CO2 GHGs are directly proportional with the corresponding changes in temperature. References Ganesh PHR. 2011. Global Warming/Green House Effect. Indian Journal of Science and Technology [Print]. [cited 2012 Mar 22]; 4:3. Global Warming [Internet]. 2008. Stanford University: Solar Center: [cited 2012 Mar 22]. Available from: http://solar-center.stanford.edu/sun-on-earth/glob-warm.html Global Warming [Internet]. 2010. Cambridge (MA): Union of Concerned Scientists: [cited 2012 Mar 22]. Available from: http://www.ucsusa.org/global_warming/ Global Warming [Internet]. 2010. New York (NY): The New York Times: [cited 2011 Mar 22]. Available from: http://topics.nytimes.com/top/news/science/topics/globalwarming/index.html Goel A, Bhatt R. 2012. Causes and Consequences of Global Warming. International Journal of Life Sciences Biotechnology and Pharma Research [Internet]. [cited 2012 Mar 24]; 1:1. Available from: http://ijlbpr.com/download.php?file=jlbpradmin/upload/ijlbpr_4f0b16d501a83.pdf&iid=94 Hansen J, Makiko S, Ruedy R, Lacis A, Oinas V. 2000. Global warming in the twenty-first century: An alternative scenario. Proceedings of the National Academy of Sciences of the United States of America [Internet]. [cited 2012 Mar 23]; 97:18. Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC27611/ How Does Carbon Dioxide Cause Global Warming? [Internet]. 1994. Michigan State University: [cited 2012 Mar 23]. Available from: http://www.pa.msu.edu/sciencet/ask_st/083194.html Huber M, Knutti R. 2011. Anthropogenic and natural warming inferred from changes in Earth’s energy balance. Nature Geoscience [Internet]. [cited 2012 Mar 23]. Available from: http://www.iac.ethz.ch/people/knuttir/papers/huber11natgeo.pdf Lean J, Rind D. 1998. Climate Forcing by Changing Solar Radiation. Journal of Climate [Internet]. [cited 2012 Mar 23]; 11. Available from: ftp://iamg09.stanford.edu/pub/dunbar/IODP%20Adelie%20Drift%20and%20Holocene%20Relevant%20Papers/Lean%20J%20Climate%201998.pdf Nordell B. 2003. Thermal Pollution Causes Global Warming. Elsevier [Internet]. [cited 2012 Mar 22]; 38. Available from: http://www.ltu.se/cms_fs/1.5035!/nordell%20gpc%20vol%2038%20issue%203-4.pdf Patterson NR. 2011. Global Warming: A Critique of the Anthropogenic Model and its Consequences. Geoscience Canada [Internet]. [cited 2012 Mar 22]; 38:1. Available from: http://www.pgw.on.ca/pdfs/GlobalWarming.pdf Rao UR. 2011. Contributions of changing galactic cosmic ray flux to global warming. Current Science [Internet]. [cited 2012 Mar 23]; 100:2. Available from: http://www.friendsofscience.org/assets/documents/Rao-GCR_GW.pdf The Hidden Cost of Fossil Fuels [Internet]. 2010. Cambridge (MA): Union of Concerned Scientists: [cited 2012 Mar 22]. Available from: http://www.ucsusa.org/clean_energy/technology_and_impacts/impacts/the-hidden-cost-of-fossil.html Trimarchi, M. The Top 10 Worst Effects of Global Warming [Internet]. 2012. Discovery: Curiosity.com: [cited 2012 Mar 23]. Available from: http://curiosity.discovery.com/topic/pollution/worst-effects-global-warming11.htm Read More