European colonizers who arrived in the Americas caused death and disease to the point that it sparked what some have called the first major human-induced change in the Earth’s climate, a new study has found.

The study, conducted by researchers at the University College London (UCL), found that the arrival of European settlers killed nearly 56 million indigenous people over the course of roughly 100 years, causing large areas of farmland to go abandoned and reforested.

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The study said the new swath of vegetated land, which CNN reported was roughly the size of France at the time, caused a massive decrease in carbon dioxide (CO2) in the atmosphere.

Levels of carbon in the atmosphere had changed so much that it caused the planet to experience a global chill in 1610 that is now known as the Little Ice Age, researchers said.

"CO2 and climate had been relatively stable until this point," UCL geography professor Mark Maslin, one of the co-authors behind the study, told CNN on Friday. "So, this is the first major change we see in the Earth's greenhouse gases."

Maslin told CNN that he and the team of researchers conducted the study by examining archaeological evidence and historical data and analyzing Antarctic ice, which can trap atmospheric gas and reportedly reveal the quantity of carbon dioxide that was in the atmosphere long ago.

He said a combination of all of the above showed researchers how the reforestation that was brought on by the mass slaughter of indigenous people in the Americas led to the global chill.

"The ice cores showed that there was a larger dip in CO2 [than usual] in 1610, which was caused by the land and not the oceans," Alexander Koch, the lead author of the study, told CNN.

"For once, we've been able to balance all the boxes and realize that the only way the Little Ice Age was so intense is ... because of the genocide of millions of people," Maslin added.