There is some reason to think the Little Ice Age was an effect of Europeans invading the Americas. In particular, of bringing Eurasian diseases. Story is, plag

There is some reason to think the Little Ice Age was an effect of Europeans invading the Americas. In particular, of bringing Eurasian diseases. Story is, plagues made civilization collapse on two continents, and trees grew back where they lived, farmed and ranched. All that carbon going into tree trunks came out of the air, cutting greenhouse effect and cooling the Earth. A good plague might achieve that today. Or civilization collapsing.