Five years after the worst U.S. offshore oil spill, the industry is working on drilling even further into the risky depths beneath the Gulf of Mexico to tap massive deposits once thought unreachable.

But critics say energy companies haven't developed the corresponding safety measures to prevent another disaster or contain one if it happens — a sign, environmentalists say, that the lessons of BP's spill were short-lived.

U.S. President Barack Obama said Saturday that climate change poses the world's biggest single threat.

"Today, there's no greater threat to our planet than climate change," Obama said in his weekly address, which had an environmental theme to mark Earth Day on April 22.

A method for detecting toxins through the reactions of fish embryos has won Chinese company Vitargent International a top prize for inventions, organizers said Friday.

The Grand Prix at the International Exhibition of Inventions of Geneva went to Vitargent, from Hong Kong, for the natural method of finding toxins.

Canada revised its greenhouse gas emission data from 1990 to 2013 in a report Friday, showing it had higher carbon dioxide discharges each year, and a doubling of emissions from its oil sands.

All previous years were revised upward by around 12 to 24 megatons, which left total emissions up by 18 percent since 1990, according to the national report made under new reporting guidelines of a UN climate change agreement.

Way back in 1999, before he became China's prime minister, Wen Jiabao warned that water scarcity posed one of the greatest threats to the "survival of the nation".

Sixteen years later, that threat looms ever larger, casting a forbidding shadow over China's energy and food security and demanding urgent solutions with significant regional, and even global, consequences.

SpaceX's unmanned Dragon cargo ship arrived Friday at the International Space Station, carrying a load of food and supplies for the astronauts living in orbit.

European Space Agency astronaut Samantha Cristoforetti grappled the capsule with the space station's robotic arm at 6:55 am (1055 GMT) as the space station flew over the northern Pacific to the east of Japan, NASA said.

Vietnamese customs have seized elephant tusks and rhino horns worth millions of dollars on the black market from a flight arriving from France, officials said Friday.

The haul weighed around 65 kilograms (143 pounds) and included 18 pieces of elephant tusk and three rhino horns, which are believed to have come from Africa, a customs official told Agence France Presse.

After years of orbiting Mercury, NASA's Messenger spacecraft will crash into the planet at the end of this month.

NASA announced Messenger's impending demise Thursday. But instead of mourning, scientists and engineers celebrated the success of this first spacecraft to orbit the planet closest to our sun.

Mexico is greatly expanding a protected area of the Gulf of California and boosting navy patrols in an effort to save the vaquita marina, a small porpoise facing imminent extinction.

A report by a panel of international scientists warned last year that there were fewer than 100 vaquitas remaining, down from 200 specimens in 2012, and the animal could vanish by 2018.

When a 50-foot sperm whale washed ashore on a beach south of San Francisco, people stopped to look, snapped pictures of the massive mammal and even reached out and touched the creature that looks more like a dark ocean rock than the largest tooth predator on earth.

Biologists and veterinarians, however, had a different plan. They arrived early Wednesday morning at Mori Point on the south end of Sharp Park State Beach in Pacifica to begin the necropsy and the arduous process of cutting up the carcass for removal. The next steps remain murky.