There is legitimate conversation on both sides of climate change, with most 2017 Democrats+Republicans(Politicians and general public alike) accepting that Climate Change is real, and it is only a matter of how much of it is reasonably caused by humans and how much of it can reasonably be slowed down/reversed by humans. I'm not gonna debate the specifics on each side, but I do happen the lean towards the right on this one, we literally don't know how much human activity affects climate versus other planetary/weather like systems that are currently in play.
Anyways, this context was necessary in showing that Trump probably understands this very basic analysis. However, he is still likely to turn down the deal. Why?
My Opinion: Because the US does not have the advantage that most other dictatorships have(counting Russia here as well even if it's not an extreme example)...those dictatorships have cultivated a reputation, over a very long period of time, that they do not bluff. Yes, that's it. Simple.
In general most presidents elected to the USA have not been extremists by any sense. Trump may not be extreme in policy, but in conduct he is - just as impactful. But that's Trump, not the USA. These are different entities. The USA's reputation is not Trump's reputation. Certainly not after 5-6 months, and probably not even after 4 years. When it comes to the principled non-bluff decisions that Trump is going to have to make on Russia, North Korea, etc, he is going to ahve to have his opponents believe he will not bluff.
But he is up against the general reputation of the USA that does not immediately evaporate once he got elected. We have a reputation as pushovers, and no it's not just Obama, in general the US has been willing to compromise and bend over backwards, financially, militarily, politically, just to maintain peace. I could go on but you should get the point by now. He can very well help Climate Research/Projects later on, but this is an instance where almost every significant nation, leader, expert, politician, celebrity, CEO, is going against him. It is an opportunity to cultivate a new impression of America.
Whether you think that is important may be another conversation.