Reuters: US Secretary of State John Kerry urged UN nations on Friday to reach a deal to cut the use of a family of powerful greenhouse gases and take a big step towards keeping global warming in check. Officials from nearly 200 countries are meeting this week to hammer out an agreement to cut the use of hydrofluorocarbons (HFCs), which are used in refrigeration, aerosols and air conditioning, by amending the landmark Montreal Protocol. The Montreal Protocol succeeded in slashing the use of chlorofluorocarbons...