I think the most honest likelihood is that he's being self indulgent. He knows that his own personal component of the climate problem is infinitesimal in the big picture, whereas the diminishment of his own personal pleasure if he were to act more appropriately would be very substantial, so he indulges himself. I'm not defending that from a moral perspective. I just don't consider it at all likely that he doesn't believe what he's saying. In a similar way, one can think we should spend more on the poor of Africa without selling one's worldly possessions and giving that money to them.