...I'll be taking part on the "no" side of this debate.
" " marks to help your clarity.
When people think of global warming, they
picture a giant hole in the ozone layer and blinding sunlight ...
Well, about Gore... no, you are not attacking his character. You are pointing out the fact that Discovery debunked his claims. It is okay, I think!
About rhetorical devices... google this: rhetorical devices list
Your teacher probably taught about them in class. I am not sure how to help, because I don't know what was covered in class. Did you talk about logos, ethos, and pathos? Try this: virtualsalt.com/rhetoric.htm.
I'm not arguing that Global Warming isn't real. --- this is a rhetorical device called "concession." You concede a point.
Global climate changes have been occurring for centuries, and Global warming is most likely to be occurring now. But there are many evidences that suggest that temperature fluctuations are part of a natural cycle of climate change, not man-made causes. ---- this should appear near the beginning of your essay, not at the end.
What are the rhetorical devices covered in class?
You can easily use these: allusion, aphorism, appeal to authority, correction of erroneous views, concession, flattery, imagery, irony, logical reasoning.
google this: List of Rhetorical Devices