Physical Geography Turn Up The Heat For decades and decades, human factories and cars have discharged billions of tons of artificial greenhouse gases into the atmosphere, and the climate has begun to show many signs of global warming. On the other hand, some people want you to believe that global warming does not exist. There are many people are only out for personal gain and are outright liars. According to a scientist at NASA! ^0 Global warming is the single largest threat to our planet! +/- (Weier 2002).

Over the past two hundred years we seen significant changes in the effects on our environment, primarily due to humans and both their lack of awareness, or their total disregard for the effects that their actions have on the environment. Global warming is one of our toughest environmental challenges. It threatens the health of people, wildlife and economies around the world. The problem is carbon dioxide and other heat-trapping pollution. This pollution mainly comes from cars, power plants and other industrial sources that burn gasoline, coal and other fossil fuels. This matter collects like a blanket in our atmosphere.

As a result, the planet gets warmer. We can say that the amount of radiation from the sun that reaches the earth each year has been fairly consistent from year to year and century to century until recently. Thirty percent of the total solar energy that strikes the earth is reflected back into space by clouds, atmospheric aerosols, reflective ground surfaces, and even ocean surf. Seventy percent of the solar energy is absorbed by the land, air and oceans. ! ^0 The absorbed light is mostly in the form ultraviolet and near infrared solar radiation! +/- (Weier 2002). Absorption of this solar energy makes life on this planet possible.

The energy does not stay bound up forever. If it did our planet would wind up being hotter than the sun. Instead, when the rocks, air, and sea heat up, they give off thermal radiation, which escapes into space and allows it to cool down. This radiation is invisible to our eyes, but our hands can feel it radiating from a fire or a car engine. What we should be worried about now is that over the past 250 years, we have been artificially raising the concentration of greenhouse gases in our atmosphere. Factories, power plants, and cars, burn coal and gasoline and spit out a seemingly endless stream of carbon dioxide.

Power plants are the largest contributors to global warming. Every year they produce approximately 2. 5 billion tons of pollution. The second leading cause of this pollution is automobiles, which pumps approximately 1. 4 billion tons of pollution into the atmosphere each year. In addition to these, we as a human race produce millions of pounds of methane by allowing our trash to rot in landfills and by breeding! ^0 methane-belching cattle! +/- (Weier 2002).

Nitrogen-based fertilizers, which we use on almost all of our crops, release unnatural amounts of nitrogen oxide into the atmosphere. The increased concentrations of greenhouse gases have prevented additional thermal radiation from leaving the Earth. Therefore, these gases are trapping excess heat in the Earth!