If you think humans can't affect the climate, you clearly never read about the Dust Bowl. But just in case, let me show you why you're ridiculously wrong using a thought experiment... I know you like to think of the earth as this enormous ball. And there was some statistic saying all the humans in the earth could occupy Texas each with a few acres to each one. Which is cute, but the amount of space a person occupies is far more than just their own, in order to get the resources they need. Now, in the same sense, the earth we're talking about is merely the ecosphere. And it's a very shallow thing. Nothing airwise really changes much from the atmosphere where we stand and the stratosphere because of the border known as the tropopause, merely 5.6 m. on average or so (higher in tropics than at poles). Almost nothing ever changes from where we stand on the ground and a mile underground. An occasional eruption, but otherwise, our ecosphere, where all of life and all of our resources lie, is pretty much a sealed tight area very thin around the earth. If you had a basketball size globe it'd be a bit thinner than tin foil. So wrap the globe in tin foil. Now, unwrap the globe and take all that foil and wad it into a ball. Then hold it over the part of the globe where Texas is. Do you really think all those 7 billion people in that state can't pollute that small space? Because all evidence shows that we are, and we're insanely, suicidally efficient at it. And that's the point.