Suppose the world was still agrarian—no modern science, or technology, or industry, or economic growth.
What would things be like? Much like the whole world was a few centuries ago. Poor and violent. But there would also be no global warming. On the contrary, a 2000-year trend of gradual global cooling might have continued. It might have been a poor, violent, and cool world. (Admittedly only about 0.5C cooler per millennium.)
Were things headed towards an icy era until modernity switched the tracks to a new direction?
2000 years of global cooling–until recently
(h/t Scholar’s Stage)