Nobody who knows anything about climate change would say it just started changing. Climate is always changing like your blood pressure. Some climate change is catastrophic like the Permian Extinction Event or Triassic/Jurassic Extinction events. These were both caused by unprecedented increases in carbon dioxide levels due to magmatic plumes burning through the crust. Ironically, it is knowledge of the fragile stability of the climate that terrifies climate scientists. The climate changes extremely easily and has no preference for life or human civilization. Even small volcanic eruptions in the 14th century and the 6th century can be tied to the collapse of empires and global pandemics. Going back to blood pressure. It changes, but large punctual changes can be deadly. Same thing applies to our climate, civilization, and life. Regardless, life will go on. But climate is fragile and our society even more so.