As he has before, Bush acknowledged “the climate is changing” but stressed that it’s unknown why. “I don’t think the science is clear of what percentage is man-made and what percentage is natural. It’s convoluted,” he said at a house party in Bedford, New Hampshire.

“For the people to say the science is decided on this is really arrogant, to be honest with you,” he continued. “It’s this intellectual arrogance that now you can’t have a conversation about it, even. The climate is changing. We need to adapt to that reality.”

Earlier Wednesday, Obama warned in a commencement speech to the U.S. Coast Guard Academy that climate change “constitutes a serious threat to global security (and) an immediate risk to our national security.”