How is excessive content of Carbondioxide responsible for global warming?

Carbondioxide is a greenhouse gas. About 75% of the solar energy reaching the earth is absorbed by the earths surface. The rest of the heat radiates back to the atmosphere. But the heat radiated by the heated surface cannot pass freely into the space because excessive Carbondioxide in the atmosphere absorb more heat. This results in increase in the average temperature of the atmosphere. This is known as global warming.