DOHA, Qatar — Despite early cooling from La Nina, 2012 is on track to become one of the top 10 hottest years on record, with the United States experiencing extreme warmth and Arctic Sea ice shrinking to its lowest extent, the UN weather agency said Wednesday.

In a statement released at international climate talks in Qatar, the World Meteorological Organization said the ‘‘alarming rate’’ of the Arctic melt highlights the far-reaching changes caused by global warming.