The clock is ticking for Minnesota's indoor ice rinks. By 2020, the refrigerant chemical now used at half the state's 240 arenas to make ice no longer will be manufactured or imported into the U.S. as part of a global effort aimed at ridding the world of greenhouse gases linked to depletion of the ozone layer. The phaseout of the odorless gas R-22 is expected to be costly for arenas -- most of which are publicly owned -- because of an anticipated rise in its cost. After the deadline, arenas still will be able to use the refrigerant gas for...