I believe the "Cretaceous Greenhouse" would make quite a good movie, considering the massive inland seas that formed during the period over the continental shelf. The majority of people on Earth would have to move house to higher altitudes.

It's mind-boggling to consider that we increased the CO2 levels from 280 to 410 ppm during the industrial age. We went a quarter of the way to the Cretaceous super-greenhouse of 1000 ppm, with most of the change accumulating in recent decades. And we are accelerating.

It's hard to see how most complex ecosystems would survive that kind of change in just a century or so, evolution is simply not that rapid. Forget moving house, imagine a world where the only functional natural ecosystems are bacterial.

> I believe the "Cretaceous Greenhouse" would make quite a good movie, considering the massive inland seas that formed during the period over the continental shelf. The majority of people on Earth would have to move house to higher altitudes.

Many breadbasket lands are also fairly low-lying. The northern china plain is mostly under 50m. Even if it doesn't get covered in water, saline intrusion will seriously hurt it, as it's already starting to hurt countries with extensive coastlines and river deltas like Vietnam or Bangladesh.