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The Greenhouse Effect Essay, Research Paper

Introduction The Earth’s climate is the result of extremely complex interactions among the atmosphere, the oceans, the land masses, and living organisms, which are all warmed daily by the sun’s enormous energy. This heat would radiate back into space if not for the atmosphere, which relies on a delicate balance of heat-trapping gases including water vapour, carbon dioxide, nitrous oxide, and methane to act as a natural “greenhouse”, keeping in just the right amount of the sun’s energy to support life. This essay investigates the contribution of some important greenhouse gases towards the greenhouse effect and the future consequences of global warming.Gases in the atmosphere act like a blanket and trap or slow down some infrared radiation, or heat, emitted by the earth, thus keeping the earth warmer than it would otherwise be. Without it life on earth would not be possible. The “greenhouse effect” is essentially a natural process that allows the earth to be warm enough to sustain life. The greenhouse gas that is most abundant, and has the largest effect on climate, is water vapour. DIAGRAM OF GREENHOUSE EFFECT: Water vapour makes up about 97% of greenhouse gases (ghgs). The remaining 3% is composed of primarily of carbon dioxide (CO2), methane and nitrous oxide.Water vapour is present in the atmosphere in its gaseous form. It is the most abundant greenhouse gas, and the largest contributor to the natural greenhouse effect. Humans are not significantly increasing the concentration of water vapour in the atmosphere. More specifically, since warmer air can hold more moisture, models predict that global warming caused by other greenhouse gases would lead to a rise in global water vapour levels. In addition to its contribution to the greenhouse effect, water vapour plays an important role in regulating the temperature of the planet through clouds, which form when excess water vapour in the atmosphere condenses to form ice and water droplets and precipitation. Scientists have found that the four most important variable greenhouse gases, whose atmospheric concentrations can be influenced by human activities, are carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and chlorofluorocarbons (CFCs). Historically, CO2 has been the most important, but over the past several decades other gases have assumed increasing significance and, collectively, are projected to contribute to about as much to potential global warming over the next 60 years as CO2. The 1997 U.N. Kyoto Protocol on Climate Change would regulate three other trace gases: hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6), whose concentrations in the atmosphere are anticipated to grow over the long-term.For the past 150 years the atmospheric concentrations of these gases, particularly carbon dioxide, have been rising. As a result, more heat is being trapped than previous, which in turn is causing the global temperature to rise. Climate scientists have linked the increased levels of heat-trapping gases in the atmosphere to human activities. The concern is whether increasing amounts of man-made greenhouse gases may be warming the earth enough to significantly change weather patterns. Sulphate aerosols, which are key in cloud development and a component of urban pollution, are another key factor in climate change. In most cases, clouds formed on sulphate aerosols act to reflect incoming solar radiation and, in effect, offset atmospheric warming to some degree. In the stratosphere, these aerosols may also act as a catalyst for ozone depletion causing cooling, and reducing transfer of some heat to the troposphere. Atmospheric pollution may also be causing global warming. Gases such as methane and nitrous oxide come from a variety of sources, including mining, farming and waste disposal. Since pre-industrial times, concentrations of carbon dioxide, methane and nitrous oxide have grown by about 30%, 45% and 15%, respectively. Fossil fuels contain carbon; burning them creates carbon dioxide. This gas is responsible for about 60% of the enhanced greenhouse effect mainly due to its large atmospheric concentration and long atmospheric lifetime (50-200 years). Man-made global emissions of carbon dioxide are less than 4% of total (natural plus man-made) annual emissions. Coal, oil and natural gas are used to generate electricity, heat homes, power factories and run cars. All this burning releases billions of tons of carbon dioxide every year. Each year more than 30 billion tons of carbon dioxide is added to the air mainly by burning fossil fuels and cutting down and burning trees. Fossil fuels have been trapped far beneath the surface of the earth. The release of carbon dioxide from these represents an addition to the amount of carbon dioxide in the air. Once released from beneath the earth’s surface, the carbon atoms become a part of a complex and little understood series of events known as the carbon cycle. Fossil fuels such as coal, oil and natural gas were created chiefly by the decay of plants that flourished millions of years ago. Burning these fuels unlocks the carbon stored by these plants and releases it to the air as carbon dioxide.A more subtle effect is that the increased precipitation enhances rock weathering. As rain falls from sky water can react with CO2 to produce carbonic acid, which is very effective at leaching and eroding rock. The interaction of this acid with rock and clay can lock the carbon up in calcium carbonate materials that stay in the ground. Effectively, carbon can be taken out of the atmosphere and locked into the ground minerals by increased precipitation. This can lower CO2 content and thus lessen the greenhouse effect. Removal of trees means more carbon dioxide is present in the atmosphere. Tropical deforestation is the largest source at present. As trees grow they take carbon dioxide from the air through photosynthesis, and that carbon becomes stored in the body of the plant itself. Burning vegetation only increases the greenhouse effect if it is done on a massive scale without offsetting growth of replacement vegetation. Unfortunately, ongoing massive deforestation in developing nations for farming, mining and raising cattle has not been offset by planting new forests elsewhere, and therefore does currently represent a significant portion of man-made greenhouse gas emissions. It also contributes to the loss of thousands of animal and plant species every year. Deforestation accounts for about 20% of the carbon dioxide increase from human activities. Until 50 years ago most of the carbon dioxide from deforestation was released from temperate zones. Methane and Nitrous Oxide (N2O)Methane is the second most important greenhouse gas. It is estimated to be twenty-one times more effective at trapping heat in the atmosphere than carbon dioxide over a hundred-year time period. However, it has a much lower concentration in the atmosphere and atmospheric lifetime. The atmospheric level of methane has risen by 145% since pre-industrial times. The atmospheric lifetime of methane is about twelve to seventeen years. If current emissions were held constant, methane concentrations would stabilise in the atmosphere in less than fifty years. Nitrous Oxide is also an important greenhouse gas. It is better at trapping heat than both carbon dioxide and methane, and has a comparable atmospheric lifetime to the long-lived carbon dioxide. However, its sources are relatively moderate, and its concentration in the atmosphere is low. The atmospheric level of nitrous oxide has risen since pre-industrial times (about 13%). It is estimated to be 310 times more effective at trapping heat in the atmosphere than carbon dioxide over a hundred-year time period. Its atmospheric lifetime is about 120 years. Hydrofluorocarbon gases are man-made speciality gases developed as an alternative to ozone destroying chlorofluorocarbons (CFC’s). These were mainly used as coolants, cleaning and propellant gases and were blacklisted internationally in 1987. HFCs do not directly destroy ozone in the earth’s atmosphere because they do not possess chlorine. However, they contribute to global warming. The principle uses of HFC’s are refrigeration, as agents used to blow foams or insulation; solvents or cleaning agents, especially in semi-conductor manufacturing. They are 4,000 to 10,000 times more destructive than CO2. Perfluorocarbons(PFC), or Perfluorocompounds are also greenhouse gases which significantly contribute to global warming. They were also replacement gases for CFCs but result also as a by-product of aluminium smelting. PFCs also used as a purging agent for semi-conductor manufacture and small amounts are produced during uranium enrichment processes. Their global warming potential is 6,000 to 10,000 times that of CO2.The Effects of Global Warming The effects of global warming are not likely to occur before 100-150 years or so from now. Even then, the effects are not nearly as severe as once predicted. The sea level rise is predicted to be about one foot and the average global temperature change will amount to about one degree Centigrade (about two (need a symbol here) Fahrenheit).

Climate ChangeOver the next century, further unchecked increases in the atmospheric concentrations of carbon dioxide and other heat-trapping gases will cause more extreme changes in global climate patterns. Scientists are not yet able to predict precisely how much and how fast the climate will actually change. By using sophisticated computer models and a range of future scenarios, scientists project a further increase in global average surface temperature of about 1.8.F to 6.3.F (1.-3.5.C) by the year 2100. Such an increase in heat is comparable to the warming that ended the last Ice Age and with perhaps equally profound effects on climate. Evidence is already suggesting that the earth is warming. Mountain glaciers can be used as indicators of long term average temperatures because they accumulate or lose ice only very slowly in response to long term temperature changes. Old paintings, sketches, and geological debris left by glaciers indicate of glacier sizes at various times in the past. A measure of long-term warming or cooling in the region of a mountain glacier is the location in the mountain valley of the terminus or lower end of the glacier. If the glacier extends far down the valley, the climate has been cooling, if the terminus is far up the mountain valley then the climate has been warming. Rising sea levels are a natural phenomenon during interglacial periods. Sea levels have risen about 400 feet since the last Ice Age without any human-caused climate change. If all the earth’s frozen water melted, scientists say sea levels could rise about another 275 feet. Global warming could within a few years trigger an irreversible destruction of the West Antarctic ice sheet. That would raise sea levels by 5 metres world wide, and would submerge many low lying areas and important coastal cities across the world. The Intergovernmental Panel on Climate Change (IPCC) forecast, assuming a 4.5(need a symbol here) F. temperature rise as a result of doubling the concentration of greenhouse gas, raises sea levels 19 inches. Global warming also affects the weather world wide. Scientists are very familiar with the world wide damaging effects of the weather event known as El Ni o Southern Oscillation (ENSO). El Ni o is an anomalous oceanographic and atmospheric event in the equatorial Pacific Ocean that usually occurs every three to seven years and is characterised by an increase in the sea-surface temperature in the astern equatorial Pacific Ocean. Global warming is thought to cause unusually warm ocean temperatures in the Equatorial Pacific., which in turn triggers El Ni o. If global warming continues, El Ni o-like weather may become normal. Leading scientists in this field suggest should this happen, global warming might also wind up the ENSO cycle to an even more intense level.Global warming will not result in more pleasant temperatures on the earth. If global warming continues, we could also see increased risk to human health. According to a 1996 World Health Organisation report, Climate Change and Human Health, changes in the global climate could result in a substantial increase in the geographic ranges of insect-borne diseases such as malaria and dengue fever. Reduced fresh water supplies from changes in regional rain and snowfall may cause a higher incidence of some water and food born diseases and parasites. In addition, an increase in regional extreme weather events, such as heat waves, floods, and storms, could threaten human health through greater risk of death, injury, or resource shortages. The impacts of global warming on crop yields and productivity will vary considerably by region. The diagram below show vegetation patterns over the globe. Several studies show that maintaining today’s levels of agricultural productivity would be difficult; at best, this would require expensive adaptation strategies. Farmers will likely need to change crops and cultivation methods in the face of global warming. Even so, scientists expect productivity to fall in some areas, especially sub-Saharan Africa, parts of South Eastern Asia, tropical Latin America, and some Pacific island nations. These regions, where many of the world’s poorest people depend on isolated agricultural systems, face increased risk of hunger and famine.Regions of transition between biomes are very vulnerable to small changes in climate, particularly changes that occur on a short time scale compared to natural changes. For example, at the end of the last ice age, some 12,000 years ago, the temperature rose about 4.C over a period of 1500 years, which is the equivalent of 30 generations of trees having lifetimes of 50 years. By comparison, the current increase in greenhouse gases is estimated to warm the climate by 4.C in about 130 years, which is equivalent to less than 3 generations of the same trees. This rather abrupt change of temperature would alter the ability of these transition ecosystems to adapt to rapidly changing conditions. Rare species of both flora and fauna with small ranges may be vulnerable to local or global extinction. Ecosystem response to past climate change has been to shift gradually north or south depending on whether the temperature rises or falls. Barriers, such as roads, cities, and managed agricultural areas, now impede the gradual migration of ecosystems. For instance, the northward movement due to global warming of the temperate forests and their associated ecosystems in the southern US would be impeded by the agriculture, roads, and cities. A further concern for the future of ecosystems is that the projected temperature rise due to increases in greenhouse gases will make the planet warmer than it has been in the last 160,000 years, so we can’t compare future climate with climates that have occurred over this period. High-latitude regions such as the frozen tundra of northern Canada and Russia will experience higher than global-average temperature increases (if the global average temperature rise is 2.5.C, high latitude regions could experience a 5.C rise). This warming will increase the rate of the decay process and lead to yet more carbon dioxide and methane released to the atmosphere and further warming. Increases in carbon dioxide will cause some types of plants, known as C3 plants, to grow faster than other type of plants: C4 plants. This will lead to some plants being more competitive and therefore more dominant in ecosystems. Some agricultural crops, such as soybeans, are C3 plants, which will be more productive under increased carbon dioxide, while others such as corn, being C4 plants, will not benefit from this change. Increased growth rates for some crops and warmer climates for high-latitude agricultural nations, like Russia and Canada, could promote increased food production. Solutions to Global WarmingAvoiding these costly damages justifies immediate action to reduce emissions of heat-trapping gases. Increasing the efficiency of cars and vans, power plants and even light bulbs will not only help curb global warming, it will help cut air pollution, protect our wilderness and coasts from drilling and stimulate economic growth. Burning fossil fuels not only emits carbon dioxide, but also soot, smog and carbon monoxide. Reducing our dependence on fossil fuels cuts pollution and reduces the demand to drill in sensitive wilderness areas like the Arctic National Wildlife Refuge. It reduces the amount of oil we transport, lessening the chances of spills. Consumers benefit because efficiency costs less than the energy it saves and it helps the economy by cutting oil imports, which account for one-third of our national trade deficit. Nearly anything that generates or uses energy can become more efficient: industrial, street and commercial lighting and home heating and cooling. We don’t need to wait for new technological breakthroughs. Huge improvements in efficiency are possible with existing technology. The biggest individual efficiency improvement could come from increasing miles-per-gallon standards for cars and light trucks. Electricity demand could be cut by 30 to 50 percent with existing energy-saving technologies. After the initial investment, of course, energy efficiency keeps saving money year after year and continues to cut pollution. None of these improvements can happen overnight, but as they are phased in, technologies will continue to improve, costs will go down and savings will go up. Insulating commercial buildings can also yield impressive pollution reduction. One of the easiest ways for individual consumers and small businesses to save energy and money is to use compact fluorescent lights. Replacing a 60-watt incandescent bulb with a 15-watt compact fluorescent bulb that emits as much light saves over 400 pounds of coal. Scientists and economists have identified many cost-effective opportunities, including energy-efficiency measures, advanced vehicle technologies, cuts in oil and coal subsidies, and investments in clean energy sources. These strategies would yield bonus benefits by reducing local air pollution and creating high-technology jobs, while controlling the risks of global warming.


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