Check out the link below, which details fairly convincing data that both travel bookings and searches (a leading indicator of future bookings) are off sharply. Proof of causality is hard, but when travel declines sharply just after a new President takes office and starts treating foreigners very harshly ...
And don't think he'll accept the sudden 20% drop that exactly coincides with inauguration as "proof" if he doesn't accept the current 10000x larger temperature change gradient than anywhere in earth history as "manmade". It's only proof if it comes from a certified news source without liberal bias like Breitbart.
https://www.google.com/amp/s/amp.theguardian.com/travel/2017...