1817 prediction. Sounds like he was predicting for the immediate future--not almost 200 years down the road. Surely, most people know that earth has warmed and cooled down throughout history--sometimes naturally, sometimes caused by volcanoes, etc. It is almost as if the earth is breathing in and out, a function of it's continued existence.

sometimes naturally, sometimes caused by volcanoes

by volcanoes is also naturally

Global warming!