Scientists define underground climate change as a “silent danger” lurking beneath major cities. Until recently, its effects on civil infrastructure had not been thoroughly studied. Its links to groundwater contamination and even health problems such as asthma and heart attacks were known. However, a recent study from Northwestern University in the United States establishes for the first time a link between this phenomenon and the transformation of the soil beneath urban areas. (Jose Carlos Cueto, Role,BBC News World)