The jet travel may be justified, but if he believes what he is saying he should be flying commercial and the extravagance in the rest of his lifestyle looks really hypocritical.
>climate change is real
>climate change is man made
>climate hazards will impact people all over the world
>climate change quickly creates additional hazards which need to be dealt with on top of whatever problems already affect us (erosion of infrastructure, salination of farmlands/aquifers due to flooding, traffic trapping people during a forest fire)
Perhaps Al Gore believes that individual actions are completely insignificant compared to the acts of corporations and governments. Maybe he is a closet climate-denier. If either of those things are true, it is inconvenient that many see him as the face of climate activism. I think the case for climate mitigation should hinge upon scientific evidence, rather than the lifestyle and personal opinions of a single man.
It's also fairly straightforward to find people who don't exactly hold scientists in high regard.