My stratigraphy prof taught that it was due to a number of things
You're almost 90 Mr. Iowa. I'm guessing there wasn't a google when you were back in school and your teacher is long dead. Maybe you should take a senior citizen class in climate science at your local community college. Meet new friends and learn new things.
Are you dense? The problem is the speed it’s changing. What took thousands of years and enabled many species to adapt it’s now happening at a much faster pace. CO2 is at its highest level in millions of years and along with the increasing methane in the atmosphere is heating up the atmosphere at a faster rate. Humans were not around the last time this happened.