Global warming refers solely to the fact that the Earth's atmosphere is warming near its surface. Simply put, it's getting hotter. The term does not imply a cause or speak to cause. The scientific community believes climate changes like global warming have occurred throughout Earth's history and will continue to occur in the future. Some evidence links global warming to solar activity; however, there are other theories as well.

One popular theory relates to the "greenhouse effect." Gases that make up our atmosphere are analogous to a greenhouse in that they allow sunlight to pass through, then trap much of the heat from escaping. This naturally occurring phenomenon keeps Earth's surface warmer than it would be otherwise. However, human produced compounds regularly released into the atmosphere in recent years have "thickened the greenhouse wall" beyond naturally occurring levels. When this happens, even less heat escapes, causing temperature to rise. This is called greenhouse warming and results in global warming.

While the scientific community accepts global warming as a given, greenhouse warming is more controversial. Everyone agrees that human-produced compounds like carbon dioxide, methane, chlorofluorocarbons (CFC's), etc. are being released into the atmosphere, yet some argue it's not clear how this factors into the changes in global warming.

Another distinct issue commonly associated with greenhouse warming and global warming is the ozone. Ozone is a naturally occurring gas in the lower atmosphere that helps trap heat. The burning of fossil fuels creates even more ozone, as ozone is one component of smog. As ozone builds, so does trapped heat, increasing the greenhouse effect.

Additionally, ozone plays a role in the upper atmosphere where it shields the Earth from deadly ultraviolet (UV) radiation. Unfortunately, CFC's - the same human produced compound that acts like a greenhouse gas in the lower atmosphere - destroy ozone. This can result in holes in our upper ozone layer as seen over Antarctica where cold temperatures, atmospheric circulation and other factors combine to 'draw' these ozone holes.

In conclusion, global warming and the issues surrounding it have far-reaching implications and can significantly impact human life on many levels. For this reason, scientists want to know how long the Earth has been warming, at what rate is it warming, and what factors are causing it. These answers will better prepare us to handle the effects of global warming.