The Earth has been undergoing climate change continuously for billions of years.
At one point the Earth had a tropical climate, during which time dinosaurs evolved and ruled the planet for millions of years, all the way from the northernmost parts of what is now Canada down to the tip of South America. Then the Ice Age came, and the cold-blooded dinosaurs couldn't adapt, and were replaced by the rise of warm-blooded mammals. In the early middle ages, long before any coal-fired plants were releasing CO2, there was another "mini" ice age where the average temperatures dropped noticeably. And so on and so forth. How arrogant of us to believe that our activities on Earth these past, what, hundred years or so, are causing large-scale and sweeping climate change, when climate change has been the norm for billions of years... long before the first self-proclaimed Hollywood celeb or politician "expert" on climate change ever came along.