I'm going to say he was lying. When I was a child, the big "climate" scare was a new ice age. Then it was aerosol spray cans punching a hole in the ozone. Then it was as we all know global warming aka climate change. I could go on and on with all the science scares, but I don't have time. My point being that we have yet to see any of these doom and gloom predictions come true. I think Bernie is a charlatan selling snake oil just like a lot of other governmental officials. How else is he able to afford his lifestyle?
On a side note, one fear I had as a child was quicksand. Where is all of this quicksand that I saw so much of in the movies?