Climate change warning: Greenland once melted and raised the ocean 5 feet.

Twenty-five years after the Sept. 11 terrorist attacks a public opinion poll reveals a striking generational divide in what Canadians know about the world’s deadliest terror attacks, how deeply they feel its impact, how much they fear terrorism — and even on the question of whether terrorism can be justified. The poll’s findings suggest personal memories of the shock and horror of the Sept. 11, 2001, attacks change how people think about terrorism. The nationwide poll of Canadian adults, conducted this week by Leger Marketing for the Association for Canadian Studies and provided to...