Not an expert certainly, but I did teach AP biology for 8 years, before taking my current job with Obsidian. Human influence upon our climate at this point is debatable. Considering automobile/factory emissions, turning the rainforest into a parking lot, the excessive numbers of livestock, all of these have undoubtedly played at least a minor role in hastening the global warming trend. I'm too lazy (and busy! Did I mention busy!?) at the current moment to track down cites from relevant literature to back these claims up, but the really important thing to consider is this:
Regardless of how much we argue about whether or not humans influence climate change on our planet, we cannot overlook this simple fact...humans are in a state of exponential growth. In 1999, we hit 6 billion. It is projected that only 50 years from now, we will hit 9 billion. It is irresponsible and disingenuous, to think that this surplus of human growth will not have an additional impact of some sort, upon our climate.