This document discusses the history of climate change from the 19th century to present day. It details how early scientists in the 19th century began detecting small increases in global temperatures and realized emissions from burning fossil fuels could impact the climate. It describes how the science progressed throughout the 20th century and consensus grew that climate change posed a serious risk. Major studies in the 1980s and 90s definitively linked rising greenhouse gases to human activity like fossil fuel use.