Guillermo Berra, a researcher at the National Institute of Agricultural Technology, adjusts a plastic tank on the back of a cow at their farm in Castelar, on the outskirts of Buenos Aires, in this picture taken July 4, 2008. Argentine scientists are taking a novel approach to studying global warming, strapping plastic tanks to the backs of cows to collect their burps. Researchers say the slow digestive system of cows makes them a producer of methane, a potent greenhouse gas that gets far less public attention than carbon dioxide in efforts to fight global warming. Picture taken July 4, 2008. [Agencies]