CO2 emissions by human activities
Almost all greenhouse gases are caused by human activities. Usually, the total amount of greenhouse gases is expressed as carbon dioxide (in short CO2). CO2 is emitted when driving cars, taking flights, using gas at home and producing products in a factory. Most of the emitted CO2 originates from burning gas, coal and other fossil fuels (which engines need), but also deforestation, production and consumption of food and manufactured goods contribute significantly.