Global Warming
Kategorie: Biológia (celkem: 966 referátů a seminárek)
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- Přidal/a: anonymous
- Datum přidání: 01. července 2007
- Zobrazeno: 2384×
Příbuzná témata
Global Warming
Each day the sun warms the earth. Sunlight strikes the earth and heats the surface. This heat is then slowly radiated back into the atmosphere. Eventually this heat, or infrared radiation, escapes the earth’s atmosphere and returns to space. Thus, an energy balance is set up: energy input is balanced by energy output. This balance may be altered by air pollutants, notably CO2. Naturally occurring CO2 allows sunlight to pass through the atmosphere and heat the earth, but absorbs infrared radiation escaping from the earth’s surface and radiates it back to earth. This process helps maintain the earth’s temperature. Any increase in the concentration of CO2 would slow down the escape of heat.Increasing of atmospheric CO2 results in rise in global temperature and greenhouse effect. CO2 acts like a glass in a global greenhouse slowing down the escape of infrared radiation from the earth’s surface.
Scientists recently discovered that a variety of gases, found in increasing concentrations in the atmosphere, reradiate infrared radiation to earth more effectively than CO2. These include methane, nitrous oxide, and chlorofluorocarbons (CFCs). Most of these gases are from human sources, although a few like methane come from natural sources.
Rising global concentrations of CO2 are attributed to increasing global consumption of fossil fuels. If fossil fuel consumption continues to increase, between 2030 and 2050 the average daily temperature will increase by about 20 to 50 C. At first glance this increase seems insignificant. However, such a change could drastically alter global climate - it would be drier than normal.
Early atmospheric scientists noted that normal levels of carbon dioxide found in the atmosphere make the earth habitable. Without carbon dioxide, the earth would be so cool that life would probably not exist.
Like so many things in the world around us, a little carbon dioxide is good, too much may be devastating, disrupting the global climate. The signs of disruption are already beginning. Dry years brought decline in grain and wheat production, forest fires and grassland fires. Another sign that global warming has begun is the chipping off the icebergs in Antarctica, the spreading of the deserts, destroying cropland and pastures.
Global warming will make cities unbearable in the summer. Global climate modelers predict that by 2030 the number of days above 320 C will increase from 36 to 87.
Ocean communities would also suffer enormously.
By 2050, sea level is expected to rise 50 to 100 centimeters. The rise in sea level would result from two factors : (1) the melting of the glaciers and of the land-based Antarctic ice pack and (2) an expansion of the seas resulting from warmer temperatures.
Humans are not the only species that would suffer during global warming. Many plants and animal species will be wiped out. Others will suffer incredible declines in their populations. Others may adapt or migrate to suitable habitat.
The changes may result in a dangerous positive feedback. The oceans, for instance, are a major reservoir for carbon dioxide. Without the oceans, carbon dioxide levels in the air would be much higher than they already are. As the earth’s temperature rises, however, the ocean’s ability to dissolve and hold carbon dioxide falls. The ocean will then release much of the carbon dioxide they have been absorbing into the atmosphere, accelerating the rate of change.
Global warming is also the result of deforestation: the rapid loss of trees, especially in the tropics. Trees absorb carbon dioxide, which they use to produce nutrients, woody tissue and bark. Worldwide, forests are being cut much faster than they regrow. As a result, deforestation “contributes“ about one-fourth of the annual global increase in CO2. To stave off or stop the rapid increase in global temperature will require a massive reforestation of the earth. Individuals can help by recycling, building smaller homes, and supporting reforestation projects, even landing a hand to replant clear-cut areas, roadsides, abandoned fields, and backyards.
To offset the CO2 that your lifestyle creates would require you to plant 400 trees. Obviously, this seems to be impossible for most people, other measures are needed.
Energy conservation is a good one. That means walking, bicycling, or riding a bus to school or work, building smaller, energy-efficient homes, insulating existing homes, recycling, and using efficient appliances. Using renewable resources and supporting family planning can also help.