How We Know the Warming is Human-Induced: Video

Separating Human and Natural Influences on Climate

Many lines of evidence show that the warming of the past 50 years is primarily due to human activity. First, basic physics explains that greenhouse gases trap heat and thus increase temperature. Since the industrial revolution and the rapid increase in the use of fossil fuels, humans have added more than a trillion tons of carbon dioxide to the atmosphere. As a result, atmospheric concentrations of CO2 have increased by about 40 percent since then. Figure source: IPCC, Working Group I, Hegerl et al. 2007. Read more.