Greenhouse gases from human activities are the most significant driver of observed climate change since the mid th century 1 The indicators in this chapter characterize emissions of the major greenhouse gases resulting from human activities, the concentrations of these gases in the atmosphere, and how emissions and concentrations have changed over timeOn Earth, the major greenhouse gases are water vapor, which causes about 36–70 percent of the greenhouse effect (not including clouds); The gases that contribute to the greenhouse effect include water vapor, carbon dioxide (CO2), methane, nitrous oxides, and chlorofluorocarbons (CFCs) On Earth, human activities are changing the natural greenhouse Over the last century the burning of fossil fuels like coal and oil has increased the concentration of atmospheric CO 2 This happens because the coal or oil Greenhouse Effect Vector Art Icons And Graphics For Free Download Greenhouse gas effect clipart