New Scientist: THE world's coldest capital might seem an unlikely spot for a geoengineering experiment designed to cool things down. But even though the average year-round temperature in Mongolia's capital, Ulan Bator, is close to freezing, the city has to endure sizzling summers coupled with deadly air pollution a combination that has forced the government to try a novel remedy. In November 2011, engineers began to drill a network of holes across 30 hectares of land north of the city and fill them with water....