求英文演讲稿,关于温室效应的
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发布时间:2022-05-26 07:15
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热心网友
时间:2023-05-01 05:01
The term "greenhouse effect" can be a source of confusion as actual greenhouses do not function by the same mechanism the atmosphere does. Various materials at times imply incorrectly that they do, or do not make the distinction between the processes of radiation and convection
The term 'greenhouse effect' originally came from the greenhouses used for gardening, but as mentioned the mechanism for greenhouses operates differently. Many sources make the "heat trapping" analogy of how a greenhouse limits convection to how the atmosphere performs a similar function through the different mechanism of infrared absorbing gases
A greenhouse is usually built of glass, plastic, or a plastic-type material. It heats up mainly because the sun warms the ground inside it, which then warms the air in the greenhouse. The air continues to heat because it is confined within the greenhouse, unlike the environment outside the greenhouse where warm air near the surface rises and mixes with cooler air aloft. This can be demonstrated by opening a small window near the roof of a greenhouse: the temperature will drop considerably. It has also been demonstrated experimentally (Wood, 1909) that a "greenhouse" with a cover of rock salt heats up an enclosure similarly to one with a glass cover Greenhouses thus work primarily by preventing convection; the atmospheric greenhouse effect however reces radiation loss, not convection
Global warming: Causes, effects, solution and outcome
One of the greatest threats faced by the world today is the rising global temperature. There are many factors, which contribute to global warming. However, we can help minimise the increasing temperature by adopting some effective measures..
CJ: Prakash Kini , 1 Apr 2008 Views:7924 Comments:9
THE PROBLEM: Through the use of fossil fuels and the release of greenhouse gases, the earth’s temperature rises in a process known as global warming.
The causes: Global warming is caused by the burning of carbon rich fossil fuels, which in its consumption, release carbon dioxide – a green house gas – that when released into the atmosphere builds up and allows the heat that enters the atmosphere to collect, and the earth’s temperature to rise. Other greenhouse gases include methane, nitrous oxide, and sometimes, even water vapour can act as a green house gas.
The effects: The effects of global warming are most obviously the warming of the globe, but this can have many unforeseen side effects, such as the melting of some of the earth’s ice stored in it’s poles and it’s glaciers, such as the Greenland Ice Sheet, a rise of three to four degrees Fahrenheit could cause up to 40 per cent of the earth’s costal areas to be enveloped by the rising oceans. The global temperature has risen between 0.45 to 0.6 degrees Celsius and the oceans have risen between 15-20 cm in the last century e to global warming and the instrial revolution.
The solution: We can solve this problem by recing the amount of carbon dioxide emissions emitted by our cars and factories, carpooling, using bikes and developing alternative fuel sources could rece these emissions on the personal level. However, getting the power generating companies and other instries to stop using fossil fuels would take a lot of time and would be hard to do. Many independent and government groups are working to solve this problem. One such governmental effort is the Kyoto Protocol, a plan devised by a group of national governments working in to stop global warming.
The outcome: If we ignore these problems, we could have serious ecological problems like the rising of the oceans e to the melting of the ice caps or the disturbance of many fragile ecosystems that rely on a carefully moderated temperature.
I hope that this information has provided some insight into the causes, effects and ways to stop global warming.
What is Greenhouse Effect ?
The ¨Greenhouse Effect〃 is a term that refers to a physical property of the Earth's atmosphere. If the Earth had no atmosphere, its average surface temperature would be very low of about -18� rather than the comfortable 15� found today. The difference in temperature is e to a suite of gases called greenhouse gases which affect the overall energy balance of the Earth's system by absorbing infra-red radiation. In its existing state, the Earth-atmosphere system balances absorption of solar radiation by emission of infrared radiation to space (Fig. 1). Due to greenhouse gases, the atmosphere absorbs more infrared energy than it re-radiates to space, resulting in a net warming of the Earth-atmosphere system and of surface temperature. This is the ¨Natural Greenhouse Effect〃. With more greenhouse gases released to the atmosphere e to human activity, more infrared radiation will be trapped in the Earth's surface which contributes to the ¨Enhanced Greenhouse Effect〃.
参考资料:http://zhidao.baidu.com/question/2008337.html?si=10
热心网友
时间:2023-05-01 05:02
The world economy has run into a brick wall. Despite countless warnings in recent years about the need to address a looming hunger crisis in poor countries and a looming energy crisis worldwide, world leaders failed to think ahead. The result is a global food crisis. Wheat, corn and rice prices have more than doubled in the past two years, and oil prices have more than tripled since the start of 2004. These food-price increases combined with soaring energy costs will slow if not stop economic growth in many parts of the world and will even undermine political stability, as evidenced by the protest riots that have erupted in places like Haiti, Bangladesh and Burkina Faso. Practical solutions to these growing woes do exist, but we'll have to start thinking ahead and acting globally.
The crisis has its roots in four interlinked trends. The first is the chronically low proctivity of farmers in the poorest countries, caused by their inability to pay for seeds, fertilizers and irrigation. The second is the misguided policy in the U.S. and Europe of subsidizing the diversion of food crops to proce biofuels like corn-based ethanol. The third is climate change; take the recent droughts in Australia and Europe, which cut the global proction of grain in 2005 and '06. The fourth is the growing global demand for food and feed grains brought on by swelling populations and incomes. In short, rising demand has hit a limited supply, with the poor taking the hardest blow.
So, what should be done? Here are three steps to ease the current crisis and avert the potential for a global disaster. The first is to scale-up the dramatic success of Malawi, a famine-prone country in southern Africa, which three years ago established a special fund to help its farmers get fertilizer and high-yield seeds. Malawi's harvest doubled after just one year. An international fund based on the Malawi model would cost a mere $10 per person annually in the rich world, or $10 billion in all. Such a fund could fight hunger as effectively as the Global Fund to Fight AIDS, TB and Malaria is controlling those diseases.
Second, the U.S. and Europe should abandon their policies of subsidizing the conversion of food into biofuels. The U.S. government gives farmers a taxpayer-financed subsidy of 51¢ per gal. of ethanol to divert corn from the food and feed-grain supply. There may be a case for biofuels proced on lands that do not proce foods--tree crops (like palm oil), grasses and wood procts--but there's no case for doling out subsidies to put the world's dinner into the gas tank.
Third, we urgently need to weatherproof the world's crops as soon and as effectively as possible. For a poor farmer, sometimes something as simple as a farm pond--which collects rainwater to be used for emergency irrigation in a dry spell--can make the difference between a bountiful crop and a famine. The world has already committed to establishing a Climate Adaptation Fund to help poor regions climate-proof vital economic activities such as food proction and health care but has not yet acted upon the promise.
What is true for food will be true for energy, water and other increasingly scarce resources. We can combat these problems--as long as we act rapidly. New energy sources like solar thermal power and new energy-saving technologies like plug-in hybrid automobiles can be developed and mobilized within a few years. Environmentally sound fish-farming can relieve pressures on the oceans. The food crisis provides not only a warning but also an opportunity. We need to invest vastly more in sustainable development in order to achieve true global security and economic growth