Rio Tinto’s half-year profit has slumped 34 per cent following weaker commodity prices, and the $US5.7 billion ($8.4 billion) underlying profit and $US1.77 per share interim dividend have fallen short of analyst expectations.

Net earnings were lower at $US5.1 billion after Rio took $US800 million of impairments against its Australian alumina refineries, partly because of the challenges imposed by the country’s new carbon policy.