Swedish climate activist Greta Thunberg sailed into New York today for a United Nations summit after a 15-day journey across the Atlantic in a zero-carbon yacht.

The 16-year-old was photographed waving at journalists and well-wishers as she neared the end of her 3,000-nautical-mile (5,550 kilometers) trip.

"Land!! The lights of Long Island and New York City ahead," she tweeted early on Wednesday alongside a dark, blurry photo of lights in the distance.

Her yacht later anchored off the entertainment district of Coney Island in Brooklyn to clear customs and immigration.

The UN sent a flotilla of 17 sailboats, one for each of their sustainable development goals for 2030, to meet her for the last short leg of her journey.

She made the trip to New York to attend a UN summit on zero emissions next month after refusing to fly there because of the carbon emissions caused by planes.

The visit sees her bring her environmental message for the first time to the United States.

Greta was offered a ride on the Malizia II racing yacht skippered by Pierre Casiraghi, the son of Monaco's Princess Caroline, and German round-the-world sailor Boris Herrmann.

The yacht left Plymouth in southern England on 14 August and the teenager marked the first anniversary of the start of her school strike on 20 August.

Greta, who was diagnosed with Asperger syndrome at the age of 12, began sitting outside the Swedish parliament in August 2018 to get members of parliament to act on climate change.

She was quickly joined by other students around the world, as word of her strike spread through the media, and the "Fridays for future" movement was born.

The 18-meter yacht features state-of-the-art solar panels on its deck and sides, and two hydro-generators provide the vessel's electricity.

The crew endured cramped and rudimentary conditions onboard, eating freeze-dried food and using a bucket as a toilet.

The teenager 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 also received criticism and abuse for her uncompromising attitude.

Her voyage sparked controversy after a spokesman for co-skipper Herrmann told Berlin newspaper TAZ that several people would fly into New York to help take the yacht back to Europe.

Mr Hermann himself will also return by plane, according to the spokesman.

Team Malizia's manager insisted, however, that the young activist's journey would be climate neutral, as the flights would "be offset".

Greta has said that she does not yet know how she will return to Europe.

Ahead of the UN summit on 23 September, she will take part in youth demonstrations, before heading to Canada, Mexico and then to Chile for another UN conference in December.