Background

     The earth is similar to a greenhouse. In a greenhouse, energy from sunlight comes in through the glass and the infrared rays are trapped inside as heat. This enables plants to grow even when the air outside of the greenhouse is too cold. The earth’s atmosphere can be compared to the glass of a greenhouse. Sunlight comes in through the atmosphere and some is converted to heat. Some of this heat escapes back into space, but the rest is trapped by certain gases in our atmosphere, warming the air. This process is called the greenhouse effect. The earth’s greenhouse effect is nothing new. It has been happening since our planet’s atmosphere evolved into being. In fact, without the warming effect of the atmosphere, living things would not be able to survive. Life on this planet owes its existence to the natural greenhouse effect.

   Not all gases in the atmosphere contribute to the greenhouse effect. The main gases that trap heat are called greenhouse gases. These include: water vapor, carbon dioxide, chloro-fluorocarbons (CFCs), methane, and nitrous oxides. Several of these gases have been components of our atmosphere for thousands, even millions, of years, while others are more recent and human-made, such as CFCs. However, in the past century, since the Industrial Revolution, the relative proportions of these gases in the atmosphere have been increasing.

     One of the major greenhouse gases is carbon dioxide (CO₂). CO₂ is a natural part of our atmosphere as it is exchanged between animals and plants in the respiration - photosynthesis cycles. When living things decompose, the carbon contained in their bodies is released into the atmosphere as CO₂. Sometimes, those living things don’t decompose quickly but are trapped beneath the earth’s surface and over millions of years become fossil fuels, such as oil, coal and natural gas.

     Until not too long ago, the atmospheric CO₂ concentration has been in balance. However, CO₂ has been increasing in our atmosphere for several reasons, thus changing this delicate balance. First of all, it is the product of the combustion of fossil fuels such as oil, coal and gasoline. When fossil fuels are burned, CO₂ is released into the atmosphere. Our consumption of fossil fuels has increased steadily in the past century and thus, so has the level of CO₂ in the atmosphere.

     Secondly, carbon dioxide is released by the burning of living plants. As millions of trees in tropical rainforests are cleared and burned to make way for agriculture, more and more CO₂ is released into the atmosphere. Plants act as a natural sink for CO₂, and therefore as we remove trees and other vegetation from our earth, we are tampering with the earth’s natural ability to balance the CO₂ level. When living plants are destroyed, less CO₂ is removed from the atmosphere by the natural process of photosynthesis. Thus the destruction of the world’s forests is a double-edged sword - we are producing more CO₂ from the burning of tropical rainforests and at the same time, taking away the most important sink for CO₂.

     Another major sink for CO₂ is the ocean. The phytoplankton in the ocean are responsible for using approximately 25% of the CO₂ in our atmosphere. Unfortunately, the increasing pollution of our oceans is decreasing the populations of phytoplankton, and thereby the ability of our oceans to take in CO.₂

                                                                                                                                                                                                                   Scientists believe that the increase in the concentration of CO₂ in the atmosphere, along with other greenhouse gases, will cause more of the sun’s heat to be trapped in our atmosphere, thereby increasing the earth’s average temperature. This effect is called global warming. Over the past century, the average global temperature has risen by about 1 °F. Although this does not seem like a great increase, it may be enough to cause significant changes to our world.

   The fact that the earth’s temperature is only about 9°F warmer than during the last Ice Age puts our recent increase into perspective. It is estimated that if current CO₂ emission trends continue, the average global temperature may increase by 3 to 10°F in the next half century.

     The rate at which global warming occurs may have significant effects on the planet. Many scientists believe that as atmospheric temperatures rise, the polar ice caps will undergo a certain amount of melting. Combined with the increase in the temperature of the oceans, this may result in an increase in sea levels, drastically affecting coastline communities. Secondly, weather patterns will change throughout the world with dry areas becoming drier, and wet areas becoming wetter. Thirdly, the change in climate will occur so quickly that ecosystems that have slowly evolved in the current climate may not have sufficient time to adapt and this may result in massive extinctions.

     As we can see, the prospect of global warming and its consequences are somewhat frightening. We can, however, slow the trend by reducing our consumption of fossil fuels and using cleaner sources of energy, such as solar and wind power. As individuals, we can choose to reduce our energy consumption by using more efficient automobiles, walking, cycling or car-pooling when possible and by not buying products from industries that produce greenhouse gases.

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