Ok Ros here i go...
Green house gases are great they make this planet warm enugh for life to be habitable. what they do is block heat from going off into space, so that the heat stays here and warms our planet. Many things cause green house gases, such as landfills make methane, volcano's are one of the biggest contributers but even trees during respiration, and again when we burn them more co2 goes into the air. Humans are the unbalance here. Any amount of CO2 unnaturally made is the problem. we are making the excess amount. the past houndred years our temp has raised 1 degree from global warming, and the hottest years were in the 90's, the next century is going to be between 2-8 degrees raise, (im farienhight.) we are the unblance in global warming, ever since the agricultural and industrial age we've been making more and more green house gases. we need to change our power sources and recycle more.