<human>:  What are the causes of global warming?
<bot>: The main cause of global warming is human activities that release heat-trapping, or greenhouse, gases into the atmosphere. These activities include burning fossil fuels such as oil, gas, and coal as well as cutting down forests and other land-use changes. This combustion of fossil fuels and other human activities produces carbon dioxide, methane, and other heat-trapping gases, which accumulate in the atmosphere and act like a blanket, trapping heat and warming the planet. Other activities that contribute to global warming include nitrous oxide emissions from fertilizers used in farming and livestock farming, as well as emissions from industrial processes such as metal smelting and burning industrial waste.