Home > How the Earth Works > Energy and Our Future (1) Why global warming happens?

How the Earth Works

Energy and Our Future

(1) What is Energy?

Do you know what energy is? Energy is the power to carry out an action, like to move or carry something.

In order to perform different actions in our daily lives, like running, jumping, and thinking, we humans need "food" as our source of energy.

In a similar way, energy is used to transport people by car, to provide buildings with light and heat, and to make machinery move.

Common sources of energy that we use every day are taken from natural resources. There are two kinds of natural resources: unlimited and limited resources.

Here's one example of an unlimited resource. We all get warm when we sit in the sun, right? This heat comes from the sun's power, or "solar" energy. You could sit out in the sun every day and this solar energy would never run out. Other unlimited energy sources generate energy from the wind, water, the earth's heat (geothermal energy), and waves in the ocean.

Now, how about the resources used in gas heaters? When we use gas heaters, we burn gas made from petroleum, a natural resource taken from beneath the Earth's surface. Petroleum and coal are both natural resources that were made through the process of plants and animals breaking down, or "decomposing," over millions of years. They take so long to restore naturally that when we dig them out and use them up, they are lost for good.

We also need to think about whether or not we are producing carbon dioxide (CO2) when we use energy. Burning petroleum, coal, and natural gas all produce CO2 and release it into the atmosphere. And CO2 is a major cause of global warming. By contrast, other energy sources like solar, wind, and hydro (water) power are not a direct source of CO2.

Another thing we need to think about is where our energy sources are coming from. Is the energy resource you are using available in your own country or does your country need to buy and import it from other countries? If your country depends on imported resources, it could potentially run out of energy in an emergency.

In order to become "energy independent," or not need resources from other countries, it is important for every country to increase its "energy self-sufficiency ratio." The energy self-sufficiency ratio is the amount of energy a country can generate from resources within its own borders (also called "domestic" resources).

Energy Self-sufficiency Ratio of Each Country (Excluding 2007 data, and those about nuclear power generation)
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