Carly Rae Jepsen is canceling her performance at the Boy Scouts of America Jamboree because of the scouts' exclusion of gays.

Jepsen said Tuesday on Twitter that "as an artist who believes in equality for all people" she's pulling out of the July gathering. The event, held once every four years, is expected to draw more than 45,000.

New U.S. government figures show the amount of heat-trapping carbon dioxide in the air jumped dramatically in 2012, making it very unlikely that global warming can be limited to another 2 degrees (1.2 C). Many governments set a 2-degree increase as the upper limit.

Scientists say the rise in CO2 reflects the global economy revving up and burning more fossil fuels, especially in China.

Ancient, mummified camel bones dug from the tundra confirm that the animals now synonymous with the arid sands of Arabia actually developed in subfreezing forests in what is now Canada's High Arctic, a scientist said Tuesday.

About 3.5 million years ago, Strathcona Fiord on Ellesmere Island's west-central coast would have looked more like a northern forest than an Arctic landscape, said paleobotanist Natalia Rybczynski of the Canadian Museum of Nature in Ottawa.

The Smithsonian's National Museum of Natural History has an addition to its famous gem collection: It is a butterfly brooch made of 2,300 gems.

The "Royal Butterfly Brooch" was created in 2009 by Taiwanese jewelry artist Cindy Chao. She is donating the piece to the museum, making it the first Taiwanese-designed item in the National Gem Collection. It goes on display Wednesday.

A recently discovered comet is closer than it's ever been to Earth, and stargazers in the Northern Hemisphere finally get to see it.

Called Pan-STARRS, the comet is passing within 100 million miles (160. million kilometers) of Earth on Tuesday, its closest approach. The ice ball will get even nearer the sun this weekend — just 28 million miles (45 million kilometers) from the sun. That's within the orbit of Mercury.

Nearby the big city rumbles, but one feels almost transported to a quiet forest village when standing amid a colony of Finnish wooden houses in Warsaw's government district.

The homes, erected as temporary housing in the destroyed capital just after World War II, have dwindled over the years from 90 to about 25. Now the surviving structures have become a point of contention between their inhabitants and a city government keen on tearing them down to make way for new developments.

Hip-hop artists including rappers Nas and Somalia-born K'naan will take center stage in an unexpected place next year: as part of next season at the Kennedy Center in Washington.

The center announced Tuesday that its 2013-2014 season would include the week long festival "One Mic: Hip-Hop Culture Worldwide." It will also feature an international theater festival featuring works from at least 10 different nations and new American works in theater, opera and music.

Holding a 3-0 lead from the away leg, it seems only a total collapse by Juventus against Celtic can prevent the Italian team from booking a place in the Champions League quarterfinals.

Juventus is expected to finish off the job at home in the return leg of its last-16 matchup on Wednesday, and the players have been urging against complacency.

North Korea vowed Tuesday to cancel the 1953 cease-fire that ended the Korean War, citing a U.S.-led push for punishing U.N. sanctions over its recent nuclear test and ongoing U.S.-South Korean joint military drills.

North Korea's Korean People's Army Supreme Command warned of stronger additional countermeasures in a statement that came amid reports that Washington and North Korean ally Beijing have approved a draft of punishing sanctions for a U.N. Security Council resolution responding to North Korea's Feb. 12 nuclear test. The draft is expected to be circulated at the U.N. this week.

Pete Sampras believes tennis is free of performance-enhancing drugs now, as well as during his 14-year pro career that ended in 2002.

The winner of 14 Grand Slam titles said other than "a random case here and there" he doesn't see the top players engaging in doping.