I think he's simplifying the point in order to get it across to the reporter. The larger point is that high tides will be higher than before in many places due

I think he's simplifying the point in order to get it across to the reporter. The larger point is that high tides will be higher than before in many places due to the warmer temperatures. This means that the average sea level relative to the shore line is higher than before. He's not referring to the entire body of all the worlds oceans which is a separate thing.