Hansen is about 70 yr. old.
I'd say he'd be safe in making predictions for things beyond about 2050. That way no one can prove him wrong while he is alive.
2050?! I think 2030 would be far enough. I doubt he's going to live to 110, unless making b.s. pseudo-scientific predictions that are little better than the progostications of a carnival psychic with a crystal ball somehow grants exceptional longevity.
I predict that he's worm food by 2025, at the very latest.