Why do we need to store CO2?

We humans are putting 27 gigatonnes of Carbon dioxide (CO2) into the atmosphere every year. (A gigatonne equals 1 billion tonnes.) This is causing global warming and climate change.

So we do need to store it instead of releasing it every time we burn fossil fuel in cars and industry. The best way to store CO2 is in forests and trees, so there is a worldwide movement to plant more trees and stop cutting them down.

Some attempts have been made to pump CO2 into old mines and empty oil wells, but there are many problems with this sequestering, including huge costs and leaking well. Nowhere is this method (sometimes known as clean coal) being used successfully and economically.