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Steam and smoke are emitted from a coal-fired power station in the England. See more green science pictures.

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Imagine a scenario where an evil super-genius finds a way to suck all the oxygen out of the air, then buries it in the ground. Sound like the stuff of comic books? Well, yes, if we're talking about oxygen. But scientists are working on a way to do just that with carbon dioxide. Why capture carbon dioxide from the air? To combat global warming.

Carbon dioxide (CO2) is a natural gas that allows sunlight to reach the Earth but also prevents some of the sun's heat from radiating back into space, thus warming the planet. Scientists call this warming the greenhouse effect. When t­his effect occurs naturally, it warms the Earth enough to sustain life. In fact, if we had no greenhouse effect, our planet would be an average temperature of minus 22 degrees Fahrenheit (minus 30 degrees Celsius) [source: UNEP]. Sure, the skiing might be great, but we'd all be too dead to enjoy it.

Yes, carbon dioxide and the greenhouse effect are necessary for Earth to survive. But human inventions like power plants and transportation vehicles, which burn fossil fuels, release extra CO2 into the air. Because we've added (and continue to add) this carbon dioxide to the atmosphere, more heat is stored on Earth, which causes the temperature of the planet to slowly rise, a phenomenon called global warming.

Carbon dioxide isn't the only greenhouse gas (GHG). Others include water vapor, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons and sulfur hexafluoride. Scientists estimate that global GHG emissions due to human activities increased 70 percent between 1970 and 2004. Carbon dioxide emissions alone grew 80 percent in the same period [source: IPCC]. Many researchers believe that the process of carbon capture and storage can help us to get this number down to a healthy level.

Carbon capture involves trapping the carbon dioxide at its emission source, transporting it to a storage location (usually deep underground) and isolating it. This means we could potentially grab excess CO2 right from the power plant, creating greener energy.

In this article, we'll look at some of the existing and emerging carbon capture and storage methods. How could a device snatch CO2 out of the air? And where in the world is it stored? Keep reading to find out.