Global Warming 101

Actor Leonardo DiCaprio shares what he believes is the most pressing environmental issue of our time: global warming. And Leo's definitely not alone—many scientists have been warning the public for years that the Earth is getting hotter. Some say that if drastic measures aren't taken to stop it, global warming may cause catastrophic results for the billions of people living on our planet.

Leo says global warming is not only the number one issue affecting the environment—it's one of the most important issues facing all of humanity. "It's something that's going to affect not only us, but our children and our grandchildren…and generations to come," says Leo.