How do water vapour carbon dioxide and methane cause global warming?

Water vapour, carbon dioxide and methane are all greenhouse gases. This means they absorb heat rising from the surface of the earth (infrared radiation). Human activity (burning fossil fuels (coal, oil and natural gas) and bad farming practices, mostly), is adding more carbon dioxide (CO2) and methane (CH4) to the atmosphere, so more heat is captured. This is global warming.