Simply you can say that green house system is all about the ozone layer or you can about the O3 layer which is mostly helping us to decrease the temp. of the Earth or it work like mirror it only allow some amount of sunlight to pass from it and the rest of the sunlight will reflect from it which cause that the less amount heat to come on the Earth .But now a time the pollution make our ozone layer weak which causes global warning And at last you can also give some points on global warning and say the we if ozone layer is doing so mich for us then can't we do a little and then say some points to protect ozone layer. I wish it may help you if not alot then just a little