I still think you should moe this sentence to the beginning:
I'm not arguing that Global Warming isn't real. Global climate changes have been occurring for centuries, and Global Warming is most likely to be occurring now. But there is a great deal of evidence, which suggests that temperature fluctuations are part of a natural cycle of climate change, not man-made causes.
This is a key argument in the speech.
Matt, this new version looks good, but I think you could cover more than you do. Cram a lot of info into each paragraph for a concentrated orange juice essay. I'll give some of my thoughts below.
I am a firm believer in the theory that Human action is mostly responsible for global warming.
Much as your essay tries to argue the reverse to my believe it is good food for thought.
The speech seems well prepared but am yet to be convinced.
In this situation, you are supposed to refute some points instead of just saying you disagree.
Challenge yourself to make a counter argument.
Global warming is a tough one to take a stance on, though, because we know that a lot of money is involved and that researchers often try to find something significant where none exists, just to validate their research. But... on the other hand, we should be reducing harmful emissions for other reasons, even if global warming is not human-made!
On one hand, we have a lot at stake if global warming is being caused by humans. We don't want to accidentally destroy the planet. But on the other hand, we have only been measuring temperature for a small amount of time in human history.
And look at all these experts disagreeing. I am not even an expert, so I feel that I have no place in the argument. Nevertheless, if I can get a car that runs on water, I will. ;-)