He is afraid of being proved wrong. It's a very common problem with climate change deniers. Facts and figures keep piling up but they always grasp any possible alternative explanation. The longer they sustain their position, the fooler the look if they backtrack, so they tend to become more and more entrenched in their opinions. Trump just happens to have the opportunity to silence government funded organizations.
Thing is that once you accept climate change as man made event, the immediate consequence is asking all the businesses to spend extra on minimizing impact. That never goes well with businesses. My theory is that republicans initially started denying climate change due to lobbying and then they had to take that as religion because science doesn't support it.
This is why there's been a push towards the "climate change" wording in the first place.
That's because, in a mistaken campaign to get people motivated, AGW activists say "See how hot it is today? Global warming is the reason!" Remember how the northern ice cap was supposed to be gone by 2013? Polar bears extinct?
If you don't want people on the other side to make arguments based on today's weather, you have to call out the people doing it on your side.
[long string of anti-science tweets]
I'm not sure what your point is exactly? That it was a "joke" but he also believed it? Because he says in that "admission":
>And I often joke that this is done for the benefit of China — obviously I joke — but this done for the benefit of China.
So is he saying its for the benefit of China or not? At best it seems that he's trying to say it but weasel out of any accountability for saying it.
I think splitting hairs over the term is unnecessary. I'm sure there are people who believe earth's climate has always been the same but they are probably very few. The most popular position among climate change deniers, as far as I know, is that this changes are part of the natural cycle and humans have little or no impact.
As long as one can say that mankind should not take any action to avert climate change, most "climate deniers" are happy, and whether the myriad of supporting arguments contradict each other is not their concern.
For example, what's Trump's opinion on whether the Earth is warming or not? Does he even care?