universe is getting older, others believe it is due to the greenhouse effect.

 The greenhouse effect is a naturally occuring phenomenon that is responsible for trapping heat near the earth's surface and keeping the planet warm. It is called the greenhouse effect because the way it works is similar to the way in which a green house functions. In a greenhouse sunlight passes through the transparent roof and walls and strikes the objects inside- plants, flowerpots, tables, and so forth. These objects absorb energy from sun, become warmer, and then give off energy themselves in the form of heat. Only a little of this heat energy passes out through the glass, much of it is "trapped" in the greenhouse, raising the temperature inside.

In some ways, the earth functions rather like a greenhouse except on a much larger scale.

Although the greenhouse effect has only recently been in the news, is nothing new in th history of our planet, has played major role in making life on earth possible. Without the greenhouse effect, the earth would be too cold for living

The greenhouse effect occurs when gases such as methane, carbon dioxide, nitrogen oxide and CFCS trap heat in the atmosphere by acting as a pane of glass in a car. The 'glass' lets the sunlight in to make heat, but when the heat tries to escape, the gases reabsorb it. Holding this heat in causes heat waves, droughts and climatic changes which could alter our way of living. The greenhouse effect, in environmental science, is a popular term for the effect that certain variable constituents of the Earth's lower atmosphere have on surface temperatures. "It has been known since 1896 that the Earth has been warmed by a blanket of gases. The gases; water vapour (H2O), carbon dioxide (CO2), and methane (CH4) keep ground temperatures at a global average of about 15 degrees C." (Oppenheimer, p. 119-120) Without them, the average would be below the freezing point of water. The gases have this effect because as incoming solar radiation strikes the surface, the surface gives off infrared radiation, or heat, that the gases trap and keep near ground level. Environmental scientists are concerned that changes in the variable contents of the atmosphere, particularly changes caused by human activities, could cause the Earth's surface to warm up to a dangerous degree. "Since 1850 there has been a mean rise in global temperature of approximately 1 degree C." (Gribbin, p. 14) Even a limited rise in average surface temperature might lead to at least partial melting of the polar icecaps and hence a major rise in sea level, along with other severe environmental disturbances.

The Cretaceous Period occurred over 100 million years ago. It was the warmest period we have knowledge of yet. There was so much carbon dioxide in the air that the oceans rose many metres. North America was flooded and split apart into two pieces. The temperature then was more than fifteen degrees greater than the average temperature today.

Over the last 100 years the global temperatures have been increasing slowly but steadily. "Since 1980 the temperature has risen 0.2 degrees C each decade." (Clayton, p. 113) Scientists predict that if we continue putting the same amount of gas into the atmosphere, by the year 2030 the temperature will be rising by as much 0.5 degrees C or more per decade. Overall, the global temperature could rise anywhere from 5 to 9 degrees over the next fifty years.

Some common words found in the essay are:
Issue Statement, Ice Age, Everglades Florida, North America, Topographic Experiment, greenhouse effect, Cretaceous Period, carbon dioxide, global warming, water vapour, earth's surface, Word Count, ice caps, average temperature, sea level, climatic changes, fossil fuels, polar ice caps, ice caps melt, Greenhouse Effect, sea levels rise, water vapour carbon, vapour carbon dioxide,
Approximate Word count = 2288
Approximate Pages = 9 (250 words per page double spaced)