"July was the hottest the world's oceans have been in almost 130 years of record-keeping. ... Meteorologists said there's a combination of forces at work this year: A natural El Nino system just getting started on top of worsening man-made global warming, and a dash of random weather variations. The resulting ocean heat is already harming threatened coral reefs. It could also hasten the melting of Arctic sea ice and help hurricanes strengthen."