The phenomenon can happen naturally, so we can't possibly cause it? Comforting!

Actually, the phenomenon has to happen naturally. If it did not, the planet would be completely dead -- like our own Moon. We, and the rest of Earth life, keep the world alive -- ironically.

Comparing human activity on this little speck against the effect of the universe on other planets is all well and good -- but we cannot simply choose to disallow nature when associating the same argument with Earth.

We do have an effect, but miniscule when compared with geothermal activity. As a result, our own contributions to global warming has probably allowed us to survive here for the past few millennia.

We have recently turned vast regions of the Amazon basin into concrete deserts, but we have also irrigated vast regions of desert into productive farmland.

The Pac-Rim is strewn with volcanic activity, only one of which spews forth fluorocarbons to the upper atmosphere far more effectively than all our most potent factories combined, including the entire fleet of active SUVs.

NASA sat-shots show the main source of the world's pollution to be grass fires in Africa, and coal furnaces (domestic and commercial) in China.

Dan