What is the global warming potential of water vapor? Are the anthropogenic water vapor emissions significant?
Water vapor is a very important part of the Earth’s natural greenhouse gas effect and the chemical species that exerts the largest heat trapping effect. Water has the biggest heat trapping effect because of its large concentration compared to carbon dioxide and other greenhouse gases. Water vapor is present in the atmosphere in concentrations of 3-4% whereas carbon dioxide is at 387 ppm or 0.0386%. Clouds absorb a portion of the energy incident sunlight and water vapor absorbs reflected heat as well.
