Human activity was affecting the climate long before the industrial revolution and global warming, a study to be published in the March edition of Quarternary Science Reviews asserts. After Europeans colonized the Americas in the 1500s and early 1600s and wiped out about 90 percent of the indigenous population, the earth went through a “Little Ice Age” that peaked in the 17th century and was partially caused by human activity. “It was a drastic change in the earth’s system,” Alexander Koch, the study’s lead author and a researcher at the University College London Department of Geography, told The New York Times. New vegetation that grew where humans used to live pulled additional carbon dioxide out of the atmosphere leading to a global cooling, hitting its peak in the 17th century, according to the report. Global temperatures dropped over one degree Fahrenheit and famines were common across Europe. Though volcanic activity and weaker solar rays also contributed to cooling, researchers estimate that human activity was about half of what caused the Little Ice Age.