evidence: Humans cause climate change. How do we know? 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. [...] We know that warming and cooling have happened in the past, long before humans were around. Natural "climate drivers" include the energy from the sun; aerosols from periodic volcanic eruptions, dust, and salt spray; natural ecological phenomena like methane-emitting termite mounds and CO2 uptake by plants; and variations in snow and ice cover that change how much the Earth’s surface reflects the sun’s energy back into space (referred to as albedo).