Paris jazzed up the Eiffel Tower with a multicolored, disco-style light display as the world basked in New Year's festivities with hopes that 2010 and beyond will bring more peace and prosperity.
From fireworks over Sydney's famous bridge to balloons sent aloft in Tokyo, revelers across the globe at least temporarily shelved worries about the future to bid farewell to "The Noughties" _ a bitter-tinged nickname for the first decade of the 21st century playing on a term for "zero" and evoking the word naughty.
In New York City, hundreds of thousands of revelers gathered in chilly weather in Times Square to usher in the new decade. Organizers were preparing 3,000 pounds (1,360 kilograms) of confetti that will be scattered when the New Year's Eve crystal ball drops at midnight.
Fireworks were set off at about 6 p.m. and the gigantic ball was lowered into place in preparation for midnight. Many people wore conical party hats and 2010 glasses that blinked colorfully, and some were jumping up and down to keep warm _ the National Weather Service said the temperature will be in the low 30s and forecast snow for around midnight.
Las Vegas prepared to welcome some 315,000 revelers with fireworks from casino rooftops, a traffic-free Las Vegas Strip and toasts at nightclubs from celebrities including actress Eva Longoria and rapper 50 Cent.
Even as some major stock market indexes rose in 2009, the financial downturn hit hard, sending many industrial economies into recession, tossing millions out of work and out of their homes as foreclosures rose dramatically in some countries.
"The year that is ending has been difficult for everybody. No continent, no country, no sector has been spared," French President Nicolas Sarkozy said on national TV in a New Year's Eve address. "Even if the tests are unfinished, 2010 will be a year of renewal," he added.
German Chancellor Angela Merkel warned her people that the start of the new decade won't herald immediate relief from the global economic ills. South Africa's president, Jacob Zuma, was more ebullient, saying the World Cup is set to make 2010 the country's most important year since the end of apartheid in 1994.
At midnight in Rio de Janeiro, about 2 million people gathered along the 2.5-mile (4 kilometer) Copacabana beach to watch a huge fireworks display and listen to dozens of music acts and DJs.
The multitudes came mostly dressed in traditional white clothing, a nod to the Afro-Brazilian religion of Candomble but a custom followed by nearly everyone as it is thought to bring peace and good luck for the coming year.
Officials said about 12,000 police were on duty during the New Year's Eve party in and around Copacabana to provide security.
Dressed in white and holding a glass of champagne in his hand, visitor Chad Bissonnette, 27, a nongovernmental group's director from Washington, D.C., said, "This year was the toughest I've experienced _ for the first time as an American I saw many friends lose jobs and businesses in my neighborhood close regularly."
Australian Prime Minister Kevin Rudd hailed events in 2009 like the inauguration of the United States' first black president, and international attempts to grapple with climate change and the global financial crisis.
"The great message from 2009 is that because we've been all in this together, we've all worked together," Rudd said in a New Year's message.
Australia got the some of the festivities rolling, as Sydney draped its skies with explosive bursts of crimson, purple and blue to the delight of more than 1 million New Year revelers near the harbor bridge.
Concerns that global warming might raise sea levels and cause other environmental problems were on the minds of some as the year ended.
Venice revelers rang in the New Year with wet feet as high tide on its archipelago peaked just before midnight to flood low-lying parts of the city _ including the St. Mark's Square.
The last year also offered its reminders of the decade's fight against terrorism, wars in Iraq and Afghanistan, and more recently, rising militant violence in Pakistan.
Prime Minister Gordon Brown of Britain, in a statement Wednesday, suggested that terrorism book-ended the decade, with the Sept. 11, 2001, attacks in the United States, and foiled plot by a Nigerian man to set off explosives on a U.S.-bound airliner on Christmas Eve.
"In late December we were reminded at this decade's end, just as we were at its beginning, that there is a terrorist threat which puts our safety and security at risk and which requires us to take on al-Qaeda and the Taliban at the epicentre of global terrorism," he said.
The American Embassy in Indonesia warned of a possible terrorist attack on the resort island of Bali on New Year's Eve, citing information from the island's governor _ though local security officials said they were unaware of a threat.
In a more upbeat theme, the Eiffel Tower was decked out for its 120th anniversary year with hundreds of multicolored lights along its latticework. It was seemingly retro in style, but decidedly 21st century as it showered the Iron Lady in a light show billed as more energy-saving than its usual sparkling lights.
Police blocked off the Champs-Elysees to vehicle traffic as partygoers popped champagne, exchanged la bise _ the traditional French cheek to cheek peck _ or more amorous kisses to celebrate the New Year.
Spain rang in the start of its six-month presidency of the European Union with a sound and light show illuminating Sol square in Madrid and images from the 27 member states projected onto the central post office building.
Partiers braved the cold _ and a shower from sparkling cava wine bottles _ in traditional style by eating 12 grapes, one with each tolling of the city hall bell.
Despite frigid temperatures, thousands gathered along the River Thames for fireworks were fired from the London Eye attraction just as Big Ben struck midnight _ an hour after continental western Europe.
Europe and the Americas may have partied harder than Asia. Islamic countries such as Pakistan and Afghanistan use a different calendar; China will mark the new year in February.
Still, in Shanghai, some people paid 518 yuan ($75) to ring the bell at the Longhua Temple at midnight and wish for new-year luck. In Chinese, saying "518" sounds like the phrase "I want prosperity."
Saudi Arabia is one of the few countries where New Year's Eve is not celebrated publicly. Clerics in the ultraconservative country say Muslims can only observe their faith's feasts of Eid al-Fitr and Eid al-Adha. For them, any other occasions are considered innovations that Islam rejects.
Unlike many Islamic countries where pigs are considered unclean, New Year's in Austria just isn't complete without a pig-shaped lucky charm _ and stalls selling the little porkers did a good business Thursday. Some are made of marzipan or chocolate; others come in glass, wood, rubber or soap.
Herbert Nikitsch of the University of Vienna's Institute of European Ethnology said the porcine phylactery may originate from the fact that pigs represented food and sustenance for farmers in preindustrial times.
Some festivities went awry.
In the Philippines, hundreds of people were injured by firecrackers and celebratory gunfire during the celebrations. Many Filipinos, largely influenced by Chinese tradition, believe that noisy New Year's celebrations drive away evil and misfortune _ but some carry that belief to extremes.
At Zojoji, one of Tokyo's oldest and biggest Buddhist temples, thousands of worshippers released clear, helium-filled balloons to mark the new year. Nearby Tokyo Tower twinkled with white lights, while a large "2010" sign glowed from the center.
Tokyo's Shibuya area, known as a magnet of youth culture, exploded with emotion at the stroke of midnight. Strangers embraced spontaneously as revelers jumped and sang.
In Istanbul, Turkish authorities deployed some 2,000 police around Taksim Square to prevent pickpockets and the molestation of women that have marred New Year celebrations in the past. Some officers were under cover, disguised as street vendors or "even in Santa Claus dress," Istanbul Gov. Muammer Guler said.
In Stonehaven, on Scotland's east coast, the fireballs festival _ a tradition for a century and a half _ saw in the New Year. The pagan festival is observed by marchers swinging large, flaming balls around their heads. The flames are believed to either ensure sunshine or banish harmful influences.
In contrast to many galas worldwide, the Stonehaven Fireballs Association warned those attending not to wear their best clothes _ because "there will be sparks flying along with smoke and even whisky."
Associated Press writers Bradley Brooks in Rio de Janeiro, Suzan Fraser in Ankara, Turkey, Veronika Oleksyn in Vienna, Harold Heckle in Madrid, Daniela Petroff in Venice, Rohan Sullivan in Sydney, Jay Alabaster and Tomoko Hosaka in Tokyo, Cara Anna in Beijing, Gregory Katz in London, and Jim Gomez in Manila, contributed to this story.