The scientific consensus on climate change's origins in human activities has begun to influence international law and corporate policies. Suitable for MBA and undergraduate students, this technical note is a compilation that replaces a three-part series of the same name (UVA-ENT-0036, -0037, and -0038) International concern over global climate change began in the late 20th century, when scientists saw a correlation among increasing atmospheric concentrations of certain gases, human activities emitting those gases, and an unusual increase in global ambient temperature readings. The scientific community was joined by international policy makers who had grown concerned about reports of climate change impacts ranging from melting polar icecaps to regional flooding, drought, and extreme-weather events. While a small number of scientists disagree, most researchers suggest that prudence requires action to reduce human contributions to atmospheric pollutants that cause the greenhouse effect.