Jubilant crowds will bid farewell to the hottest year on record Sunday, closing a turbulent 12 months marked by clever chatbots, climate crises, and wrenching wars in Gaza and Ukraine.

The world's population — now over eight billion — will see out the old and usher in the new, with many hoping to shake the weight of high living costs and global tumult.

In Sydney, the self-proclaimed "New Year's capital of the world", more than a million partygoers are expected to pack the city's foreshore, despite uncharacteristically dank weather.

Eight tons of fireworks will light the fuse in 2024, a year that will bring elections concerning half the world's population and a summer Olympiad celebrated in Paris.

The last 12 months brought "Barbiegeddon" at the box office, a proliferation of human-seeming artificial intelligence tools, and a world-first whole-eye transplant.

India outgrew China as the world's most populous country and then became the first nation to land a rocket on the dark side of the moon.

It was also the hottest year since records began in 1880, with a spate of climate-fuelled disasters striking from Australia to the Horn of Africa and the Amazon basin.

Perhaps more than anything, 2023 will be remembered for Hamas's October 7 assault on southern Israel — and Israel's ferocious reprisals.

Rebuilding

The United Nations estimates that almost two million Gaza residents have been displaced since Israel's siege began — about 85 percent of the peacetime population.

With once-bustling Gaza City neighborhoods reduced to rubble, there were few places left to mark the new year — and fewer loved ones to celebrate with.

"It was a black year full of tragedies," said Abed Akkawi, who fled the city with his wife and three children. 

The 37-year-old, now living in a UN shelter in Rafah, southern Gaza, said the war had obliterated his house and killed his brother.