Here's an interesting article about it: https://www.smithsonianmag.com/science-nature/how-climate-ch...
The key factor, apparently, was "... an enormous spasm of volcanic activity in the 530s and 540s CE, unlike anything else in the past few thousand years. This violent sequence of eruptions triggered what is now called the ‘Late Antique Little Ice Age,’ when much colder temperatures endured for at least 150 years."
(New theories should always be taken with a grain of salt, but I found it interesting either way.)
That requires strong political leadership and buy in.
American needs to turn back into the country represented by Captain America. They need to be leaders again, instead of acting like they're being run by one of those infant English kings from the Middle Ages..
Brr... The problem is that making quick money on scale seems to me like some kind of condition. Some biological hoarding gene that made sense just a hundred years ago.
Evolution have not kept up with our success at building and automating stuff made from stars. It makes me sad.
What we need to do is to update the rules of Capitalism to internalize the externalities. Make carbon expensive. Make environmental destruction expensive. Make exploiting labor expensive.
Do that and you'll see extremely rapid changes for the good. Only it will never happen because the people and countries currently profiting from coal / oil will fight it with the enormous $$ they have (and they are; people like the Koch brothers are always babbling on about how the government is run by a shadow 'deep state' - that's clearly true, and they're clearly being greased by oil money).
Politics is so short sighted that unless there's huge pressure from the masses nothing will be done, or just too little too late.
Even if the Science backing up Climate Change wasn't solid, which I think it is, what's the alternative? Take a gamble?
The Roman Civilization probably collapsed because, among other things, the climate optimum they experienced at their peak changed drastically and crops became less efficient. A joke compared to what we might be expecting in a few decades with such an overpopulated and hyper-efficient world, which is really fragile to climatic disruption.