The National Academy of Science has announced thatin the last century the Earth's surface temperature rose one degree Fahrenheit.That may not sound like much, but the warming pace sped up during the last 20years. And who is to blame? Humans. We have affected the chemical composition inthe atmosphere with the build-up of greenhouse gases (carbon dioxide, methane andnitrous oxide).

The Earth's weather and climate are influenced by the sun;the sun heats the Earth's surface which then sends energy back out into space.The greenhouse gases lock in some of the outgoing energy, trapping the heatinside the Earth's atmosphere.

Temperatures would decrease if this"greenhouse effect" didn't happen, but it also means that life wouldnot be possible. The "greenhouse effect" keeps the planet's averagetemperature at a friendly 60 degrees. On the other hand, if greenhouse gasesincrease, it will create harmful problems involving depletion of the atmosphereand much more.

Since the beginning of the Industrial Revolution,atmospheric concentrations have changed:

• Carbon dioxide increased 30%
• Nitrous oxide increased 15%
• Methane more than doubled.

The growth in these gases has improved the Earth's"heat-trapping" ability, but that's nothing to brag about. Sulfateaerosols are another ordinary air pollutant. They cool the temperature of theEarth's atmosphere by reflecting light back into space. Conversely, these harmfulair pollutants are briefly lived and tend to vary by region.

Scientistsbelieve the greenhouse gases are increasing and the theory is that the burning offossil fuels is the primary reason. The decomposition of natural matter and plantrespiration contribute over ten times more C02 than humanactivities.

Humans have increased the rate at which the temperature heatsup. We have increased carbon dioxide emissions, resulting in faster warming. Themore we use vehicles, heat homes, and power factories the more we contribute toglobal warming.

Facts and statistics provided by:http://yosemite.epa.gov/oar/globalwarming.nsf/content/Climate.html