Post hot ergo propter hot?

Over in one small voice, Peter Saint-Andre (who coined the wonderful title above; I can't take credit for it) talks skeptically about global warming:

People, the earth has been heating and cooling since the very beginning, and humans haven't had anything to do with it before, so I see little reason to think we have anything to do with it now. Can anyone prove that the twentieth century is any different from the eighth century in this regard?

I, too, agree with what Peter says: that there are natural cycles and that we're in a "warming" section of a cycle, and that it doesn't follow that every time we think there's a warming trend it's "global warming", we've caused it, and we're doomed to drown in a polar ice-cap-melting inundation. I used to get in trouble with some friends because they misunderstood my thoughts on this.

"Misunderstood", because I do actually believe that we are gorping up the environment, and that we must not only stop it, but do what we can to reverse it. And I do believe that much of the gorping we're doing could quite possibly doom us to melted ice caps and other climatic (and other sorts of) disasters. And, in fact, I do believe that some of that is happening. So I believe in global warming.

What I also believe is that we don't fully understand it. There are cycles, and we do not understand how what's happening now fits into the cycles, how our treatment of the environment is actually affecting the global climate apart from the cyclic effects, and what the real long-term results will be. I do not suggest that it's all normal and that we just relax and continue pumping out CFCs, airborne acids, and other nasty stuff. I suggest that we keep studying it until we understand enough about it to answer Peter's questions and mine; scientific skepticism is a good thing.

And I suggest that while we're studying it, we look at what's said by those who have a plausible explanation for why the twentieth and twenty-first centuries are different from the eighth, and we assume, for the moment, that they're right. That we change how we alter the air, water, and soil around us to some approximation of how we did in the eighth century, to the extent that we can (we're clearly not all willing to go back to riding horses and working the land, but there's still much we can do). And that we understand that the consequences of assuming that global warming is bunk until it's proven conclusively are much worse than the consequences of taking action and reducing our impact on the environment.