Heat-trapping gases.

The greenhouse gases contribute to the greenhouse effect.

Greenhouse gases are inescapable.

Greenhouse gases have been working with the heat from the sun to keep the earth comfortably warm for millions of years. The gases absorb some of the heat from the warmed earth and keep it from escaping into space. When greenhouse gas levels increase, as they are from recent human activity, they retain more heat and the earth warms up.

Greenhouse gases stop the transmission of infrared rays. These are the rays which carry heat away from the earth, and therefore an increase in greenhouse gases results in global warming.

Oxygen is not a greenhouse gas. It deceases the greenhouse gases.