If you made a model of the world today back in 1920, it would be comical.
Imagine you went back to say 1920 and told people that in 2020 they would be surrounded by talking televisions, phones, that we'd be sending people and ships to the moon, mars, etc. and that they could instantly talk to any person on the planet (including loved ones on the other side of the world), they would not believe you.
In the last 100 years (heck even the last 20-30) we've invented a staggering amount of new and interesting things.
In the last 100 years people created interstate highway systems, nuclear power, the internet, radio data networks, self guided weapons, self guided vehicles, robots, rudimentary AI, etc...
What if in 100 years we make fusion work (probably for space travel/war?) and then we replace the existing infrastructure with that. And what if we can do enough carbon removal or storage to solve this?
Any model that doesn't model the history altering inventiveness of humans is not an accurate model at all. It's just really fancy navel gazing.