The mining of shale gas in Canada and the United States leads to increases in the concentration of methane and ethane in the atmosphere, according to studies undertaken by the Atmospheric and Solar Physics facility of Liege (GIRPAS, Belgium). Note that methane is a greenhouse gas 25 times more potent that CO2 – that means one kg of methane in our atmosphere causes the earth to heat up 25 times more than one kilogram of CO2 (see the following article from Pour la Science (French edition of Scientific American) in July 2016.
