A climate researcher has been threatened with the sack by his employer after refusing to fly back to Germany at short notice after finishing fieldwork on Bougainville in the Solomon Islands archipelago. On Friday, Dr Gianluca Grimalda, an environmental campaigner who refuses to fly on principle, was told by his employer, Germany’s Kiel Institute for World Economy, that if he was not at his desk on Monday he would no longer have a job to return to. Instead this week he was still waiting in Buka Town, Bougainville, to embark on a cargo ship to begin his journey back to Europe, after six months studying the impact of climate change and globalisation on communities in Papua New Guinea. Grimalda said he intends to make the 22,000km (14,000-mile) return trip to Europe entirely without flying, instead travelling on cargo ships, ferries, trains and coaches – a journey he estimates will take two months, but that will, he estimates, save 3.6 tonnes of carbon emissions. “I have written to the president of my institute to tell him that I am not there today and that I’m going to travel back by ship and over land,” he said on Monday. “I’m feeling OK now, [but] some of the past days were pretty traumatic because I didn’t expect this type of behaviour from people at my institute. But I think I’ve made the right choice. “Air travel is really the fastest way to burn fossil fuels, so the fastest way to walk ourselves towards catastrophe … So from my perspective, as an individual, flying is probably by far the activity in which I use most of my carbon budget.” Grimalda has spent the past six months travelling around Bougainville, the largest island in Solomon Islands archipelago, finding out how its people have been affected by the effects of climate breakdown. Papua New Guinea, of which Bougainville is a part, is one of the countries most vulnerable to the impacts of the warming climate. In a long Twitter thread detailing his encounters, Grimalda details his meetings with islanders who have been forced to move entire villages inland to avoid rising tides, or who were desperately planting mangroves to hold back the waters. While conducting his fieldwork among the Papuans, Grimalda gave dozens of talks on the science of climate breakdown, explaining to islanders how the carbon emissions of the industrialised world were causing the disasters they faced. And he promised them he would minimise his CO2 emissions on his journey back to Europe to avoid contributing to their suffering. “White men (as we’re called here) are often referred to as giaman [liars or fraudsters in Tok pidgin, the local language],” he said on Twitter. “I don’t want to giaman.” Grimalda accepts that his return to Kiel is past due. His fieldwork was supposed to be completed in July and he was supposed to be back in Germany on 10 September. But he says he faced a number of unavoidable delays, including being held for ransom by machete-wielding bandits, thefts of his research items and difficulties getting communities to speak to him. “It takes time to build trust between communities and a ‘white man’ – as I am always referred to – so that several communities requested me to go and explain the contents of the research twice or even thrice before the start of the field work,” he said. Supporters of Grimalda say they believe the Kiel Institute is using this opportunity to retaliate against him for his taking part in civil disobedience climate protests. “It is extraordinary that a research institute threatens to dismiss a researcher for doing his job too diligently and for avoiding flying during a climate emergency,” said Julia Steinberger, professor of societal challenges of climate change at Lausanne University and a lead author of the latest International Panel on Climate Change report. “Kiel IfW seems mainly to retaliate for Gianluca’s past participation in civil disobedience on climate change with Scientist Rebellion.” Fabian Dablander, postdoctoral researcher at the Institute for Biodiversity and Ecosystem Dynamics at the University of Amsterdam, said: “What Gianluca is doing is a deeply inspiring act of breaking with business as usual. Any research institute should be lucky to have him. Instead, Kiel IfW wants to fire him. This is an utter disgrace.” A spokesperson for the Kiel Institute said it does not comment publicly on internal personnel matters. “When traveling on business, the institute supports its employees in travelling in a climate-friendly manner,” a spokesperson said.