With an Academy Award for "An Inconvenient Truth" and a Nobel Peace Prize, Al Gore is arguably the most public face associated with environmental issues today. Yet with all of the discussion surrounding climate change, global warming, greenhouse gases, renewable energy, and fuel conservation, many people don't understand the basics. These and other catchphrases are often used as shorthand when discussing the results of scientific studies, but those studies are frequently written in such a scholarly way that they're inaccessible to the average person. Here, then, are answers to five common questions about environmental issues.

1. Isn't global warming just a theory?

Global warming is a theory, but that doesn't mean it's not real. Theories are the basis of all scientific work, whether that work is in medicine, astrophysics, or climate change. The evidence scientists have collected thus far indicates that ice caps are melting at an unprecedented rate, weather patterns are changing, and that sea levels are rising. However, unlike a clinical drug trial that may last for a year, after which results are reviewed and a course of action is recommended, the potential effects of global warming are so catastrophic that humanity can't afford to wait for scientific theories to be proven correct before action is taken.

2. Don't temperatures natural fluctuate over time?

Yes, temperatures around the earth do fluctuate, but the rate at which the earth is warming is unprecedented. Scientists have concluded that the earth is heating up more quickly than at any time within the last million years, and that greenhouse gases are the culprits.

3. What are greenhouse gases?

The earth's atmosphere is made up of nitrogen and oxygen, as well as trace amounts of several different gases. These trace amounts of gas are called greenhouse gases because, as the earth absorbs heat during the day, the greenhouse gases trap the heat, preventing it from escaping into the atmosphere and preventing the earth from freezing at night. The problem is that, beginning with the Industrial Revolution, coal and petroleum (each of which is a fossil fuel) have been burned. Burning these fossil fuels releases carbon dioxide, which is a greenhouse gas. The excess greenhouse gases build up in the atmosphere, causing them to trap in too much heat.

4. What is renewable energy?

Renewable energy is energy that comes from unlimited sources. This is in contrast to coal and petroleum, which are fossil fuels that exist in a finite amount and are therefore non-renewable. Examples of renewable energy (sometimes called alterative energy) are wind, geothermal, and solar power, as well as hydropower and biofuels. As it pertains to climate change, renewable energy is not only important because we won't run out, but primarily because it doesn't emit carbon dioxide.

5. I'm only one person. Will anything I do make a difference in climate change?

Absolutely! Every person who implements changes reduces his or her carbon footprint, and thus makes a difference. Taking simple actions, like replacing incandescent light bulbs with compact fluorescent bulbs, changing your thermostat settings, cleaning your air filters, buying energy efficient appliances, and driving a fuel-efficient vehicle can make a tremendous difference. You can also contact your elected representatives and insist that your country take action to address climate change. Finally, you can work locally, spreading the word and encouraging friends, neighbors, and family members to adopt practices that reduce carbon dioxide emissions. Your actions can ultimately help to save the earth.