Whether people believe in human activity caused climate change or not seems to depend more on political persuasion more than logic or reason. The reality is lay people don't have the first clue. It's not because they're stupid (well in some cases it is) but because to actually develop a reasoned conclusion requires far more effort and investment than an individual is willing to commit to. So basically the only people who have valuable opinions regarding climate change are those who do it for living, and spend the thousands of hours reading incredibly boring studies when they're released, and who actually have the background and specific education to properly analyse that information.
You have to be pretty naive to think you can just read a scientific explanation and draw a reasonable conclusion (regardless of whether it's pro or negative). To put it as another example; I have a fairly reasonable although basic idea of how atomic theory works, the explanation makes sense to me, but for all I know it could be complete horse**** because I don't have the resources or inclination to verify it for myself. The exact same is true of climate change theories, whichever way you go on the issue, what you're doing is putting your trust into relevant camp. You don't actually have a legitimate understanding of it yourself, even if you think you do.
So essentially it boils down to who you believe - the overwhelming majority of the scientific community, or the minority who claim otherwise.
