Green House Effects

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About half of the sun's incoming energy reaches the Earth's surface. The rest is reflected back into space or is absorbed by the atmosphere. The Earth absorbs most of the energy that reaches its surface and re-emits it as heat. The atmosphere contains gases such as water vapor and carbon dioxide which absorb, or trap, some of the rising heat and return it back to Earth. This warming of the planet's surface is called the greenhouse effect. Without it, the rising heat would escape directly into space and Earth would be much colder.

The greenhouse effect keeps the Earth's average surface temperature at about 60°F (15°C). If there were no greenhouse gases in the atmosphere, the planet's temperature would be 0°F (-18°C), too cold for most life. Most of the heat radiated from the Earth's surface would be lost directly to outer space.

Mars has a very thin atmosphere with a weak greenhouse effect. Its surface is much colder than Earth's. In fact, it is frozen.Venus has an intense greenhouse effect. Its atmosphere is thick with carbon dioxide and other gases that trap heat. The surface of Venus is much hotter than Earth's , hot enough to melt lead.

However too much greenhouse effect on Earth can be harmful to human life and poses a threat to existence of all life forms. In the following pages, we will go on the illustrate how destructive human activities have contributed to the intensifying of the greenhouse effect.

Intensified greenhouse effect being the cause , will result in the worsening of global warming.

Human activities are intensifying the natural greenhouse effect. Every year we release billions of tons of heat-trapping gases to the atmosphere. In doing so, we are setting the stage for a warmer Earth. Carbon dioxide: industry, transportation, and deforestation. Transportation is a source of carbon dioxide emissions. Industry is a major source of heat-trapping gases.

Methane: rice farming, cattle, landfills, fossil fuel production. Nitrous oxide: fertilizers, sewage treatment plants Fluorocarbons: refrigerants, other industrial product

Expecting The Unexpected : "We're altering the environment far faster than we can possibly predict the consequences. This is bound to lead to some surprises." --Dr. Stephen Schneider, National Center for Atmospheric Research

Nasty Surprises: Some of the ways that Earth may respond to global warming could be gradual; others could be rapid. By continuing to add greenhouse gases to the air, we may be surprised by some nasty changes. Escaping Methane: As the Arctic warms, huge amounts of methane now frozen under the ocean and land could escape into the air. Because methane is a greenhouse gas that traps heat in the atmosphere, these added emissions could cause the Earth to warm even faster than now expected.

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