The truth is we don't know, but I think many are too arrogant to admit it.
I take measurements for a living and I know the uncertainty in a temperature measurement is fairly significant compared to the temperature increase that global warming proponents are saying that we have undergone. Now when we go to ice core samples to say what the temperature on earth was most people accept this as fact, however it is a bunch of assumptions, conjecture, and manipulating of the data to make it say what they want it to. The studies make no mention in uncertainty of the measurements and are not traceable to a NIST standard.
The truth is I can't say whether or not we are causing the earth to warm, but I can say without a shadow of a doubt that there is 99.9% politics with 0.1% science used to support the claims.
The question whether the planet is warming up isn't up for debate. Hell, all we need to do is look outside our front doors to see the signs. There are several other factors that go into the hypothesis, migration patterns of the wild and botanical species are examples. It also is happening at a quicker rate when compared to the heating and cooling trends of the past.
We are in unprecedented territory, because we have no way of measuring our impact at all. Compare it to what? We can only compare it to the fossil records of the past. We may not be 100% correct, but we do have a pretty good idea of the length of time it took for the natural heating and cooling of the planet in the past. With the accelerated rate of heating and all of the other data, it brings a plausible question of whether or not we are a factor.
You can put a frog in a vat of boiling water and the frog will jump out sensing the immediate danger. However, if you put a frog in pot of water and then heat it up to the boiling point, the frog will not jump out. It will acclimate itself to the ever increasing temperatures of the water and will eventually be boiled alive, never sensing the pending danger. Humans, as proven time and time again, react in much the same way.
We can debate until the cows come home whether or not the warming of the planet is due to human activity or not. By the time the political grand standing is done or a definitive answer is known, it may be to late.
Again.......no matter what side of the debate one is on, it does make sense to implement technology that would be better for the environment, our resources and our lifestyles.