Veks has a point, one that I debate with my husband time and time again. I take the fact that humans are effecting the environment detrimentally and need to cease and desist before its too late, and he takes the fact that there is methane gas trapped in ice in the oceans, that the volcano's let out CO2 emissions naturally, that yes there was ice ages before and warm periods.
My argument is that we are helping. Sorry, but coal burning factories are not natural. Dragging oil from the ground, refining it and burning it to emitt the same emissions is not natural. Look at the mini-ice age that occurred that is blamed for the extinction of the Mammoth, and scientist theorize that the Clovis Tribe might have disappeared due to the rapid climate change. This just proves that rapid rapid climate changes do not give anyone, or anything time to adapt, to evolve to adjust to it. Then things die.
The mini-ice age was by far the most rapid natural climate change that I am aware of, and it was not in the span of seventy years. I shudder to think what that kind of climate change will do?
I think that this climate change is a combination of both human effects on the environment and a natural climate shift. The human effects is speeding the process to dangerous speeds. Humans tend to force things to bend to their will, rather then going with the flow of what is natural (taoism yay! :) ) and eventually there is a price to pay for that behavior.
But as Vekseid said as well, even if it was completely natural there is no reason why we can not find alternative fuel sources, wind solar geothermal, why we can not start conserving? It's /slightly/ less convenient then just throwing our trash on the side of the road, or just plugging a pump into our cars every so many miles but most things worth while come from just a bit of work.