Bernama: The main cause of global warming is the high level of carbon dioxide (CO2) in the atmosphere. Therefore, to reduce it, extended green plants area is needed, experts said. “Lately, the green plants existence in the world has decreased, mostly because of human’s action. This results in the increasing of the temperature,” Antara news agency quoted Professor of the Faculty Mathematics and Physics (MIFA) University of North Sumatra (USU) Retno Widhiastuti, as saying here …