Early European explorers of North America may have indirectly triggered the Little Ice Age by exposing the local population to new diseases

By the end of the 15th century, between 40 and 80 million people are thought to have been living in the Americas. Many of them burned trees to make room for crops, leaving behind charcoal deposits that have been found in the soils of Mexico, Nicaragua, and other countries. About 500 years ago, this charcoal...