\"By sailing to the New World, Christopher Columbus and other explorers who followed him may have set off a chain of events that cooled Europe’s climate.

The European conquest of the Americas decimated the people living there, leaving large areas of cleared land untended. Trees that filled in this territory pulled billions of tons of carbon dioxide from the atmosphere, Stanford University geochemist Richard Nevle reported October 11 at the Geological Society of America annual meeting. Such carbon dioxide removal could have diminished the heat-trapping capacity of the atmosphere and cooled the climate, Nevil and his colleagues have previously reported.

“We have a massive reforestation event that’s sequestering carbon … coincident with the European arrival,” said Nevle.\"

http://www.sciencenews.org/view/generic/id/335168/title/Columbus_blamed_for_Little_Ice_Age

This fits with modern models for Climate Change Action as well. Just get rid of enough people and Gaia will heal herself.