AN ELABORATE international experiment to fertilise a swathe of the Southern Ocean has run into trouble.
Tonnes of iron dust were to be dumped into the sea from a German research ship across a 300 square kilometre area in the experiment to examine its possible use in absorbing a greenhouse gas.
With the expedition's 48 scientists already at sea planning to begin work near the Antarctic Peninsula, the German science ministry has suspended approval, Nature reported.
Smaller attempts have been made in recent years to examine whether iron dust can encourage marine algal blooms and increase the ocean's capacity to absorb carbon dioxide.
It is an unproven remedy with side effects, according to the Australian Antarctic Climate and Ecosystems Co-operative Research Centre in Hobart.
The Canadian-based ETC environment group's spokesman Jim Thomas said: "This case clearly shows why we need strong enforceable rules to prevent rogue geo-engineers unilaterally tinkering with the planet."