evidence: Scientists agree that global warming is caused mainly by human activity. Specifically, the evidence shows that certain heat-trapping gases, such as carbon dioxide, are warming the world—and that we release those gases when we burn fossil fuels like coal, oil, and gas. [...] This information tells scientists that human-caused fossil fuel emissions have been the main contributor to the rise in CO2 concentrations since the pre-industrial era. [...] Major scientific assessments also agree. The 2018 US National Climate Assessment—whose authors include 300 leading scientists and thirteen federal government agencies—concludes that "it is extremely likely that human activities, especially emissions of greenhouse gases, are the dominant cause of the observed warming since the mid-20th century. For the warming over the last century, there is no convincing alternative explanation supported by the extent of the observational evidence."