The earth was hotter during the roman periods than it was today, and was even hotter in multiple eras in The past. The earth simply goes through various temperature phases, heating up and cooling down, due to numerous factors like solar activity, core activity, etc. The only exception to this is cataclysmic events like asteroidal strikes significant enough to influence temperature.
The real issue is that they are destroying flora that covert CO2 into oxygen. I have shown NASA thermal analysis in my presentations demonstrating What happens to atmospheric carbon conditions during farming seasons, and it reveals that by simply planting more plants and trees and not cutting them down, the earth can naturally regulate the excess co2 levels and even fix the world "greenhouse gas" problem within 10-20 years.
If there is a human problem, its simply that there are too many people on the planet, thanks to modern technology, specifically petroleum based technology. Technology allows for people to live longer, which is why the world is over populated and its resources, habitats and ecosystems are consumed and destroyed.