A climate scientist on Wednesday said he was being threatened with the sack for refusing to fly back to Germany from a research trip in Papua New Guinea.

Gianluca Grimalda, a senior researcher at the Kiel Institute for the World Economy (IfW Kiel), has spent six months investigating the social effects of climate change in the Pacific island country.

Grimalda made most of the outward trip to Papua New Guinea by land and sea, taking 35 days to travel around 16,000 kilometers.

He wished to return entirely by cargo ships, ferries, trains and buses, he said in a statement shared by the campaign group Scientist Rebellion.

But the IfW Kiel is allegedly insisting approval for his trip ran out on September 10 and he must return immediately by plane.