Pregled teksta

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Seminar work in english
THEME: Global warming
Banja Luka, april 2010.
1. Introduction 3
2. Global warming 4
2.1. The Greenhouse Effect 5
2.1.1. Greenhouse gases 6 Carbon dioxide 7 Methane 8 Nitrous oxide (N2O) 9
2.2. Climate models 9
2.3. Attributed and expected effects 11
2.4. Responses to global warming 12
3. Conclusion 15
4. Literature 16
Global warming is when the earth heats up (the temperature rises).  It happens when greenhouse gases (carbon dioxide, water vapor, nitrous oxide, and methane) trap heat and light from the sun in the earth’s atmosphere, which increases the temperature.  This hurts many people, animals, and plants.  Many cannot take the change, so they die. Global warming is affecting many parts of the world.  It makes the sea rise, and when the sea rises, the water covers many low land islands.  This is a big problem for many of the plants, animals, and people on islands.  The water covers the plants and causes some of them to die.  When they die, the animals lose a source of food, along with their habitat.  Although animals have a better ability to adapt to what happens than plants do, they may die also.  When the plants and animals die, people lose two sources of food, plant food and animal food.  They may also lose their homes.  As a result, they would also have to leave the area or die.  This would be called a break in the food chain, or a chain reaction, one thing happening that leads to another and so on.
Global warming
Global warming refers to an increase in the Earth’s average surface air temperature. Global warming and cooling in themselves are not necessarily bad, since the Earth has gone through cycles of temperature change many times in its 4.5 billion years. However, as used today, global warming usually means a fast, unnatural increase that is enough to cause the expected climate conditions to change rapidly and often cataclysmically.
On an average day, this effect is caused by water vapor and clouds (75 percent) and carbon dioxide (20 percent), with the rest fthe heating caused by other gases. Relatively small additions of carbon dioxide and methane force more heat, and that heat allows the air to hold more water vapor, creating a feedback loop that magnifies the effect. Although water vapor is naturally prevalent in the atmosphere, it does not trap as much heat per molecule as carbon dioxide and methane. Also, water vapor molecules cycle through the atmosphere in only a few days, a brief period compared to the residence time of CO2, which persists for many decades and creates some warming even after as long as three hundred years. Dust and aerosol chemicals in the air cause some cooling (negative forcing); they are also very short lived. Even though the gases are measured only in parts per million (ppm) or billion (ppb), they have been powerfully, and naturally, influencing the Earth’s temperature for millions of years. Without them, instead of an average air temperature of about 58°F (14.5°C), the Earth would be below the freezing point. Life as we know it now would be impossible. Earth’s temperature is also subject to natural forcing cycles from solar radiation and the movement of the planet around the sun. Scientists think these cycles, which have left a visible signature extending back millions of years, are what led to past ice ages and the warming that ended them. Currently, we are in a period between major ice ages. The last great glaciation, when temperatures were about 10°to 12°F (6°to7°C) cooler than today, began fading away about 18,000 yearsago. The initial transition out of the ice age was unstable,with many rapid temperature shifts. As temperatures warmed, climate was affected.


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