The Chinese hoax thing was literally a joke to be in the agenda wise he may not have been joking — but he was joking with that tweet. The important thing here is Donald Trump stands with science. In the journal Nature almost every single industrialized country is not on track to meet the targets. See: Analysis in the journal Nature: ‘No major advanced industrialized country is on track to meet’ UN Paris pledges
That’s what Donald Trump is rejecting. The UN’s own leadership has called for this.