system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What to people have to gain by claiming climate change isn't happening?

Let me explain. In most issues I'm pretty Republican, but I don't understand why the Republican side is so passionate about climate change not being real. It seems to be pretty cut and dry that it's happening and I don't understand why people believe so strongly that it's not. 
So what's the political/economical/whatever upside of claiming it's not happening when there seems to be pretty strong evidence. I can't believe it's solely about greed or protecting corporations. There has to be more to it than just that.
gpt
Two really key points that need to be straightened out first before answering you.

* Very few influential people are claiming that climate change isn't happening, there's just too much evidence for it. What a number of people are doing is claiming that climate change (in the form of regional effects of global warming) is not being caused by HUMAN activity. If it's a natural process, we can't be to blame for it.

* Different people have different motivations. Some people honestly do believe that the "truth" is humans aren't causing it, either because their own research leads them to this conclusion or because they believe other people's messages and they're just conveying those opinions onward. 

So let's talk about the people who originally create those messages that others might follow, and answer your question. 

Many of those people sometimes have very strong interests in disconnecting human activity sources from climate change results. They work for or represent companies that do things like produce lots of greenhouse gas, or produce and sell non-renewal energy sources like coal and gasoline. So their livelihood depends on people not believing that they're causing a potential problem, and they do their best to try and suppress that belief.

Or they're argumentative as a job or as a hobby. A lot of the conspiracy theorists out there don't believe any messages that come from government, and apply less-than-scientific processes to their cherry-picked analysis of what the causes are. They either get their kicks doing it, or get a paycheck from doing it.