Hmm, let me guess. It has something to do with the fact that we live on planet which mostly molten lava. And you think that some of this heat is making it up to the thin skin of the planet we are accustomed to living on.
No, wait maybe something to do with radioactive heat? Ok I give up. What are you talking about?

It seems to me that Earth is mostly heated by the Sun. That most significant greenhouse gas is water. That intensity of the Sun [because the sun changes or the distance to the Sun changes] and the tilt of the axis of Earth are other major factors in changing global climate. Another major factor but more important on regional scale is terrian features- where land is, the topography of both the land and the ocean.

This whole global warming thing is a complete and utter hoax. What is significance of CO2 as greenhouse gas? There two things about CO2. One it was thought to be a significant factor in affecting ice ages and warming periods. This idea never actually was proven- it was merely a hypothses. No one knows what causes ice ages or warming- and if they did it wouldn't have anything to do with CO2. Two, CO2 was thought to cause a runaway affect- this was an even a less serious hypothesis. People who hold this brain fart often mention Venus as if there was connection between Venus [which recieves twice as much solar radiation as Earth]. From these ideas a religion has grown. AND all this crap boils down to making a story about the fucking weather- how goddamn boring can you get?
Take any desert. What's notable about desert? They lack water. If the desert is near equator and isn't miles high and isn't near a large body of water. You have hot days and cold nites- in other words on a regional scale you have little in regards to a greenhouse affect. Now, go to some sandy bare little island in the middle of the Pacific on equator. Your days may or not be as hot, but you will certainly have warmer nites than in the desert- on regional level lots of greenhouse affect. And whether the CO2 level was 380 ppm or 1000 ppm would have little affect upon this.