GENEVA (Reuters) - The earth is on track for its hottest year on record and warming at a faster rate than expected, the World Meteorological Organization (WMO) said on Thursday. Temperatures recorded mainly in the northern hemisphere in the first six months of the year, coupled with an early and fast Arctic sea ice melt and "new highs" in heat-trapping carbon dioxide levels, point to quickening climate change, it said. June marked the 14th straight month of record heat, the United Nations agency said. It called for speedy implementation of a global pact reached in Paris last December to limit...