"The natural cycle is understood by examining the paleo records. The fact that the earth goes in and out of ice ages distinctly outlines the natural cycles of Earth's climate. This occurs about every 100,000 years. We are currently in a warm period. Generally, Earth spends about 80-90,000 years in an ice age and around 10-20,000 years (or so) in a warm period."

The argument is that 10,000 years ago the earth was at its warmest. It was cooling down to an ice age, and as pointed out earlier this takes 80-90,000 years until 1750. Then it started warming up again unnaturally. The question is why would the earth warm up and cool down for millions of years on a regular cycle until 1750?

I met someone who is convinced because when he was little the summers were extra hot and the winters were extra cold just like now. He thinks the earth's natural cycle is 50 years long not 100,000 years long.

[and the Grand Canyon was formed by a river that flowed through it wore out the inside and bottom. it took 17 million years to look like that. a hundred years from now it will look the same but 50 years ago Alaska looked differently. why?]