evidence: In the 1960s, the evidence for the warming effect of carbon dioxide gas became increasingly convincing. Scientists also discovered that human activities that generated atmospheric aerosols (e.g., "air pollution") could have cooling effects as well (later referred to as global dimming). Other theories for the causes of global warming were also proposed, involving forces from volcanism to solar variation. During the 1970s, scientific understanding of global warming greatly increased. [...] - ^ a b c d e Spencer Weart (2003). "The Carbon Dioxide Greenhouse Effect". The Discovery of Global Warming.