Celliod-
I noticed your question about why global warming occurs. Since questions about the oil industry are best left in the capable hands of people like Rockman, I'll tackle your question about the environment (as that's more my specialty anyway). Basically, life on earth depends on greenhouse gases, like carbon dioxide, water vapor, and methane. Without them in the atmosphere, the planet surface would be, on average, more than 50 degrees colder than it is, and uninabitable by most life as we know it (just a few chemosynthesizers maybe, near oceanic vents). But we do indeed have the greenhouse gases, and they serve as insulators. Among all the different frequencies of radiation which the sun emits, ultraviolet strikes the surface of the earth, warms it up, and is re-radiated as lower-energy, lower-frequency infrared. The greenhouse gas molecules absorb this infrared and re-radiate it themselves, which effectively means, they reflect a portion (not all--they re-radiate some out toward space as well...and they also absorb the IR from the sun too--but their effect is a net positive on the earth's energy budget) back toward the surface of the earth. Basically, the more greenhouse gases--i.e. the higher the concentration is among the other gases--the more heat they help retain, and the warmer the planet gets.
Very warm periods in the earth's past, like the Cretaceous, from about 150 million to 65 years ago, featured dinosaurs, CO2 levels nearly four times what they are now, no polar ice caps, and a North American continent which was nearly 50% underwater, because of the Western Interior Seaway (the reason we have all those swell gas, oil and coal deposits running through the middle of our country). Carbon dioxide content matters. It has fluctuated widely during the planet's history, due to many causes, not all understood. One theory on the planet's biggest climate swings has to do with degree to which continents are plowing into each other and building mountains, which then chemically erode, removing CO2 from the atmosphere as they do, causing things to cool down. There's a decent-sized literature on orogenic climate theory.
Flash forward to now--we're burning all these organic compounds, releasing a lot of CO2 into the air, causing the atmosphere to retain more heat, most of which goes into the oceans. It's established fact that the world is quickly warming up. Overwhelming scientific consensus holds that humans are directly responsible. There are a lot of good sources of information about this on the web, but there's a lot of BS denialism too. The best source--thought not the easiest--is the Intergovernmental Panel on Climate Change, or IPCC. They've been rolling out their latest batch of reports over the last year or so. They're amazingly thorough, detailed, and long. But one I recommend to interested parties is the first installment, The Physical Science Basis. It lays out quite thoroughly the evidence behind climate change theory. It's not an easy read. For beginners, I recommend the Summary for Policymakers. If you want to invest 3-4 hours and stretch your brain a bit, try tackling the Technical Summary. It's an education in itself.
http://www.ipcc.ch/report/ar5/wg1/
