The Little Ice Age was a period of cooling between the 1300s and 1800s where average temperatures dropped by 4 degrees globally. It affected areas across the Northern Hemisphere and was coldest between the late 1500s to early 1700s. Potential causes included reduced sunspots, increased volcanic activity, and changes in ocean currents. The effects of the Little Ice Age included the demise of Viking settlements, destroyed cereal crops in Europe leading to famine and disease like the bubonic plague spreading more widely.