Drilling for Arctic oil is not viable yet, says IEA chief

International energy watchdog's new head, Fatih Birol, warns of costs and technological challenges but stops short of recommending an outright ban

Drilling for oil in the Arctic is not yet commercially viable and may not be for a long time to come, the chief of the world's energy watchdog has warned, casting doubt on the controversial practice even as it is being enthusiastically adopted by governments and businesses.

Shell is undertaking exploratory Arctic drilling off the Alaskan coast after the Obama administration granted it a green light in August. Environmental groups have urged a ban, saying it risks one of Earth's last pristine landscapes and is contributing to climate change, which this week was blamed for Arctic sea ice shrinking to its fourth lowest ever level.