1、 查看文章 英文演讲稿 环保 温室效应 the responsibility of the youth2009-08-25 20:22Good evening ladies and gentlemen,Today I want to talk about the responsibility of the youth on the environment issues.When I was young, I always dreamed about traveling around the world. One of the places that I want to visit most i
2、s the Great Barrier Reef in Australia. In my imagination, that must be a warm and clean place full of beautiful coral reefs, fishes like Nemo, kind and understanding dolphins, colorful sea turtles. They said that the Great Barrier Reef can even be seen from outer space! However, it is also said that
3、 due to the climate change mass coral bleaching events occurred in the summer of 1998,2002 and 2006, Beautiful scenery will vanish in the year 2050. That means when I am ready to pay a visit to Australia with my beautiful wife maybe, I can only see the faded coral reefs which are whiter than white.T
4、hroughout history, the young have been the driving force in social change. Now more than ever is the time for youth across the country to become global warming activists and join the movement. Youth should take the responsibility to help solve the problem as soon as possible.At a United Nations Worl
5、d summit on the world economy, Ex Premier Zhu Rongji said “economic development and environmental protection are interlinked and can not be separated from each other.” He also said, “A new pattern that guarantees a clean environment must replace the traditional pattern. That the new one is called su
6、stainable development.” But as individuals, what we can do to bid our effort in it ?Here are some tips :1. Change the lightReplacing one regular bulb with a compact fluorescent light bulb will save 150 pounds of carbon dioxide a year.2. Recycle moreIt is said that in Japan, people are requested to s
7、eparate the waste in different kinds. And the trash man would only collect one kind of waste each day. That can be a perfect way to recycle.3. Use less hot waterIt takes a lot of energy to heat water. Use less hot water by installing a low flow showerhead and washing your clothes in cold or warm wat
8、er.4. Adjust your air conditionerMoving your air conditioner just 2 degrees in winter and up 2 degrees in summer. You could save about 2,000 pounds of carbon dioxide a year with this simple adjustment.5. Plant a treeA single tree will absorb one ton of carbon dioxide over its lifetime.6. Turn off el
9、ectronic devicesSimply turning off your television, DVD player and computer when youre not using them will save you thousands of pounds of carbon dioxide a year.Global warming has already been a very serious problem in the world. Even in our generation, varieties of birds singing are silenced, beaut
10、iful coral reefs are no longer be seen. It is a real pity that when Im telling my son about the dream when I was young. He can never know a place named Great Barrier Reef.Thank you very much.英文资料-温室效应!The Greenhouse EffectThe greenhouse effect is a naturally occurring process that aids in heating th
11、e Earths surface and atmosphere. It results from the fact that certain atmospheric gases, such as carbon dioxide, water vapor, and methane, are able to change the energy balance of the planet by absorbing longwave radiation emitted from the Earths surface. Without the greenhouse effect life on this
12、planet would probably not exist as the average temperature of the Earth would be a chilly -18 Celsius, rather than the present 15 Celsius. As energy from the sun passes through the atmosphere a number of things take place (see Figure 7h-1). A portion of the energy (26 % globally) is reflected or sca
13、ttered back to space by clouds and other atmospheric particles. About 19 % of the energy available is absorbed by clouds, gases (like ozone), and particles in the atmosphere. Of the remaining 55 % of the solar energy passing through the Earths atmosphere, 4 % is reflected from the surface back to sp
14、ace. On average, about 51 % of the suns radiation reaches the surface. This energy is then used in a number of processes, including the heating of the ground surface; the melting of ice and snow and the evaporation of water; and plant photosynthesis. The heating of the ground by sunlight causes the
15、Earths surface to become a radiator of energy in the longwave band (sometimes called infrared radiation). This emission of energy is generally directed to space (see Figure 7h-2). However, only a small portion of this energy actually makes it back to space. The majority of the outgoing infrared radi
16、ation is absorbed by the greenhouse gases (see Figure 7h-3 below).Figure 7h-3: Annual (1987) quantity of outgoing longwave radiation absorbed in the atmosphere.(Image created by the CoVis Greenhouse Effect Visualizer).Absorption of longwave radiation by the atmosphere causes additional heat energy t
17、o be added to the Earths atmospheric system. The now warmer atmospheric greenhouse gas molecules begin radiating longwave energy in all directions. Over 90 % of this emission of longwave energy is directed back to the Earths surface where it once again is absorbed by the surface. The heating of the
18、ground by the longwave radiation causes the ground surface to once again radiate, repeating the cycle described above, again and again, until no more longwave is available for absorption.The amount of heat energy added to the atmosphere by the greenhouse effect is controlled by the concentration of
19、greenhouse gases in the Earths atmosphere. All of the major greenhouse gases have increased in concentration since the beginning of the Industrial Revolution (about 1700 AD). As a result of these higher concentrations, scientists predict that the greenhouse effect will be enhanced and the Earths cli
20、mate will become warmer. Predicting the amount of warming is accomplished by computer modeling. Computer models suggest that a doubling of the concentration of the main greenhouse gas, carbon dioxide, may raise the average global temperature between 1 and 3 Celsius. However, the numeric equations of
21、 computer models do not accurately simulate the effects of a number of possible negative feedbacks. For example, many of the models cannot properly simulate the negative effects that increased cloud cover would have on the radiation balance of a warmer Earth. Increasing the Earths temperature would
22、cause the oceans to evaporate greater amounts of water, causing the atmosphere to become cloudier. These extra clouds would then reflect a greater proportion of the suns energy back to space reducing the amount of solar radiation absorbed by the atmosphere and the Earths surface. With less solar ene
23、rgy being absorbed at the surface, the effects of an enhanced greenhouse effect may be counteracted.A number of gases are involved in the human caused enhancement of the greenhouse effect (see Table 7h-1 below). These gases include: carbon dioxide (CO2); methane (CH4); nitrous oxide (N2O); chloroflu
24、orocarbons (CFxClx); and tropospheric ozone (O3). Of these gases, the single most important gas is carbon dioxide which accounts for about 55 % of the change in the intensity of the Earths greenhouse effect. The contributions of the other gases are 25 % for chlorofluorocarbons, 15 % for methane, and
25、 5 % for nitrous oxide. Ozones contribution to the enhancement of greenhouse effect is still yet to be quantified. Concentrations of carbon dioxide in the atmosphere are now approaching 360 parts per million (see Figure 7a-1). Prior to 1700, levels of carbon dioxide were about 280 parts per million.
26、 This increase in carbon dioxide in the atmosphere is primarily due to the activities of humans. Beginning in 1700, societal changes brought about by the Industrial Revolution increased the amount of carbon dioxide entering the atmosphere. The major sources of this gas include fossil fuel combustion
27、 for industry, transportation, space heating, electricity generation and cooking; and vegetation changes in natural prairie, woodland, and forested ecosystems. Emissions from fossil fuel combustion account for about 65 % of the extra carbon dioxide now found in our atmosphere. The remaining 35 % is
28、derived from deforestation and the conversion of prairie, woodland, and forested ecosystems primarily into agricultural systems. Natural ecosystems can hold 20 to 100 times more carbon dioxide per unit area than agricultural systems. Artificially created chlorofluorocarbons are the strongest greenho
29、use gas per molecule. However, low concentrations in the atmosphere reduce their overall importance in the enhancement of the greenhouse effect. Current measurements in the atmosphere indicate that the concentration of these chemicals may soon begin declining because of reduced emissions. Reports of
30、 the development of ozone holes over the North and South Poles and a general decline in global stratospheric ozone levels over the last two decades has caused many nations to cutback on their production and use of these chemicals. In 1987, the signing of the Montreal Protocol agreement by forty-six
31、nations established an immediate timetable for the global reduction of chlorofluorocarbons production and use. Since 1750, methane concentrations in the atmosphere have increased by more than 140 %. The primary sources for the additional methane added to the atmosphere (in order of importance) are r
32、ice cultivation, domestic grazing animals, termites, landfills, coal mining, and oil and gas extraction. Anaerobic conditions associated with rice paddy flooding results in the formation of methane gas. However, an accurate estimate of how much methane is being produced from rice paddies has been di
33、fficult to obtain. More than 60 % of all rice paddies are found in India and China where scientific data concerning emission rates are unavailable. Nevertheless, scientists believe that the contribution of rice paddies is large because this form of crop production has more than doubled since 1950. G
34、razing animals release methane to the environment as a result of herbaceous digestion. Some researchers believe the addition of methane from this source has more than quadrupled over the last century. Termites also release methane through similar processes. Land-use change in the tropics, due to def
35、orestation, ranching, and farming, may be causing termite numbers to expand. If this assumption is correct, the contribution from these insects may be important. Methane is also released from landfills, coal mines, and gas and oil drilling. Landfills produce methane as organic wastes decompose over
36、time. Coal, oil, and natural gas deposits release methane to the atmosphere when these deposits are excavated or drilled. The average concentration of nitrous oxide in the atmosphere is now increasing at a rate of 0.2 to 0.3 % per year. Sources for this increase include land-use conversion; fossil f
37、uel combustion; biomass burning; and soil fertilization. Most of the nitrous oxide added to the atmosphere each year comes from deforestation and the conversion of forest, savanna and grassland ecosystems into agricultural fields and rangeland. Both of these processes reduce the amount of nitrogen s
38、tored in living vegetation and soil through the decomposition of organic matter. Nitrous oxide is also released into the atmosphere when fossil fuels and biomass are burned. However, the combined contribution of these sources to the increase of this gas in the atmosphere is thought to be minor. The
39、use of nitrate and ammonium fertilizers to enhance plant growth is another source of nitrous oxide. Accurate measurements of how much nitrous oxide is being released from fertilization have been difficult to obtain. Estimates suggest that the contribution from this source may represent from 50 % to
40、0.2 % of nitrous oxide added to the atmosphere annually. Ozones role in the enhancement of the greenhouse effect has been difficult to determine scientifically. Accurate measurements of past long-term (more than 25 years in the past) levels of this gas in the atmosphere are currently unavailable. Co
41、ncentrations of ozone gas are found in two different regions of the Earths atmosphere. The majority of the ozone (about 97 %) found in the atmosphere is localized in the stratosphere at an altitude of 15 to 55 kilometers above the Earths surface. In recent years, the concentration of the stratospher
42、ic ozone has been decreasing because of the buildup of chlorofluorocarbons in the atmosphere (see Lecture 7e). Since the late 1970s, scientists have discovered that total column ozone amounts over Antarctica in the springtime have decreased by as much as 70 %. Satellite measurements have indicated t
43、hat the zone from 65 North to 65 South latitude has had a 3 % decrease in stratospheric ozone since 1978. Ozone is also highly concentrated at the Earths surface. Most of this ozone is created as an artificial by product of photochemical smog.In summary, the greenhouse effect causes the atmosphere t
44、o trap more heat energy at the Earths surface and within the atmosphere by absorbing and re-emitting longwave energy. Of the longwave energy emitted back to space, 90 % is intercepted and absorbed by greenhouse gases. Without the greenhouse effect the Earths average global temperature would be -18 C
45、elsius, rather than the present 15 Celsius. In the last few centuries, the activities of humans have directly or indirectly caused the concentration of the major greenhouse gases to increase. Scientists predict that this increase may enhance the greenhouse effect making the planet warmer. Some exper
46、ts estimate that the Earths average global temperature has already increased by 0.3 to 0.6 Celsius, since the beginning of this century, because of this enhancement. Predictions of future climates indicate that by the middle of the next century the Earths global temperature may be 1 to 3 Celsius hig
47、her than today. Table 7h-1: Gases involved in the Greenhouse Effect: past and present concentration and sources.Greenhouse Gas Concentration1750Concentration1995Percent Change Natural and Anthropogenic Sources Carbon Dioxide 280 ppm 360 ppm 29 % Organic decay; Forest fires; Volcanoes; Burning fossil
48、 fuels; Deforestation; Land-use change Methane 0.70 ppm 1.70 ppm 143 % Wetlands; Organic decay; Termites; Natural gas Biomass burning; Rice cultivation; Cattle; Refuse landfills Nitrous Oxide 280 ppb 310 ppb 11 % Forests; Grasslands; Oceans; Soils; Soil cultivation; Fertilizers; Biomass burning; Bur
49、ning of fossil fuels Chlorofluorocarbons (CFCs) 0 900 ppt Not Applicable Refrigerators; Aerosol spray propellants; Cleaning solvents Ozone Unknown Varies with latitude and altitude in the atmosphere Global levels have generally decreased in the stratosphere and increased near the Earths surface Created naturally by the action of sunlight on molecular oxygen and artificially through photochemical smog production Greenhouse Effect A worldwide greenhouse effect might produce a dangerously warmer world. Since the late 19th century, the average global temper
