TORONTO - Prince Harry surprised thousands of young people Thursday when he arrived unannounced at the Toronto We Day celebration.

Harry took the stage around lunchtime at Air Canada Centre, the host venue for the youth empowerment event.

The prince spoke about the importance of optimism in a cynical world.

There are a lot of scary forces in the world right now, he said, but hope for the future should remain the most important focus.

Harry touched specifically on environmental sustainability, telling the crowd that he understands their frustration about how “entrenched mindsets are not keeping pace with the urgency of the threats to our environment.”

He also said he feels encouraged by how much young people value environmental causes.