Irreversible warming tipping point may have been triggered: Arctic mission chief

The tipping point for irreversible global warming may have already been triggered, the scientist who led the biggest-ever expedition to the Arctic has warned.

"The disappearance of summer sea ice in the Arctic is one of the first landmines in this minefield, one of the tipping points that we set off first when we push warming too far," said Professor Markus Rex.

"And one can essentially ask if we haven't already stepped on this mine and already set off the beginning of the explosion."

Prof Rex led the world's biggest mission to the North Pole, an expedition involving 300 scientists from 20 countries.

The expedition returned to Germany in October after 389 days drifting through the North Pole, bringing home devastating proof of a dying Arctic Ocean and warnings of ice-free summers in just decades.