Greta Thunberg on the Malizia II racing yacht

The team behind teenage climate activist Greta Thunberg's yacht voyage to New York on Sunday fended off claims that her trip will create carbon emissions because team members will take transatlantic flights.

The 16-year-old Swede, whose school strikes have inspired children across the world to protest against global warming, refuses to fly because of the carbon emissions caused by planes.

But she has been offered a lift on the Malizia II racing yacht, and set off on August 15 along with her father Svante and a filmmaker to document the journey, in order to attend the UN talks in September with a clear conscience.

However a spokesman for German round-the-world sailor Boris Herrmann, the yacht's co-skipper, told Berlin newspaper TAZ that several people would fly into New York to help take the yacht back to Europe. Hermann himself will return by plane, according to the spokesman.

The paper estimated that in fact Thunberg's boat trip would end up being more polluting than if she and her companions had just taken flights to New York themselves.

'An imperfect solution'

That conclusion was quickly picked up on social media sites among Thunberg's detractors.

But Team Malizia manager Holly Cova insisted that the young activist's journey would be climate neutral.

"All Team Malizia flights are offset," she said in a statement issued by Thunberg's entourage.

She explained that the New York trip had been organised "at very short notice, and as a result two people will need to fly over to the US in order to bring the boat back".

"We only have one boat, so they cannot easily sail over to meet them. Altogether, four crew will be sailing the boat back. These are logistical decisions that Team Malizia alone has taken," she added.

Cova admitted "this is an imperfect solution," adding that "the world has not yet found a way to make it possible to cross an ocean without a carbon footprint."

'I will just ignore them'

The 60-foot (18-metre) yacht is skippered by Hermann and Pierre Casiraghi, vice president of the Monaco Yacht Club and a member of the principality's ruling family.

It can travel at speeds of around 35 knots (70 kilometres an hour) but will be heading into the wind for much of the time so will be slower, and the captain wants a smooth ride.

Ahead of the UN summit on September 23, Thunberg will take part in youth demonstrations, before heading to Canada, Mexico and then to Chile for another UN conference in December. It is not clear how she will be travelling.

"I don't know yet how I will get home," she said before she set off from the English port of Plymouth.

Thunberg has become a figurehead for climate action with her stark warnings of catastrophe if the world does not act now to cut carbon emissions and curb global warming.

She has received criticism and abuse for her uncompromising attitude, but shows little concern at how she might be received among climate change deniers in the United States.

"I will just ignore them because I'm only acting and communicating the science, and if they don't like that, what have I got to do with that?" she said.