I suggest watching two movies. I recommend not forming an opinion until you have seen both.
First, An Inconvenient Truth. Then to follow, The Great Global Warming Swindle.
Personally, I believe global warming is a concern, but certainly not as bad as many make it out to be. Should we humans reduce our waste and harmful emissions? Absolutely. Should we fear the apocalypse in the next 5 years if we don't? No, I don't believe so.
Honestly, I think we should worry more about our trash situation, the state of recycling, and our obsession with plastics (see movie: Addicted to Plastics) over global warming.