A strong solar flare is blasting its way to Earth, but the worst of its power looks like it will barely skim above the planet and not cause many problems.

It has been several years since Earth has had a solar storm of this size coming from sunspots smack in the middle of the sun, said Tom Berger, director of the Space Weather Prediction Center in Boulder, Colorado. The flare on the sun barely hits the "extreme" on forecasters' scale, but with its worst effects missing Earth it is only looking "potentially strong" at most when it arrives at Earth as a solar storm, he said.

Two Russian cosmonauts and an American astronaut returned to Earth on Thursday after spending more than six months working together aboard the International Space Station, as tensions between their countries soared over the Ukraine crisis.

American Steven Swanson and Russians Alexander Skvortsov and Oleg Artemyev, who left on March 26, landed in the Kazakh steppe at 0223 GMT aboard a Soyuz capsule, the Russian space agency Roscosmos and its U.S. equivalent NASA said in statements.

Pakistan's largest city Karachi, home to around 18 million people, could be "wiped out" by a tsunami, officials said Wednesday after a drill simulating a major earthquake in the Indian Ocean.

The test, and one carried out a day earlier simulating another quake off Indonesia, were designed to check an early-warning system set up after the 2004 Indian Ocean tsunami which killed more than 230,000 people.

Wildlife campaigners in Mozambique say police have cracked an ivory poaching ring believed to be responsible for the deaths of at least 39 elephants.

Japan's nuclear watchdog Wednesday gave a green light to plans to restart two reactors, more than three years after the Fukushima disaster.

China will launch its second orbiting space laboratory in two years' time, a top official said Wednesday, the latest step in an ambitious space programme Beijing says will one day land a Chinese man on the moon.

Iconic North American birds like the Bald Eagle and Brown Pelican are among hundreds of mankind's feathered friends facing threats to their survival due to climate change, researchers said Tuesday.

The European Space Agency on Tuesday put the final touches to its first-ever "space plane" before blasting it into sub-orbit for tests aimed at eventually paving the way to the continent's first space shuttle.

Researchers Wednesday urged sailors to become "citizen oceanographers" and help scientists better understand some of the world's wildest seas where ships and even planes disappear without trace.

An Australian-led study said that despite technology such as GPS navigation and advanced research vessels with modern capabilities, much of the world's oceans remains under-explored, with cost a key impediment to knowing more.

Surging levels of carbon dioxide sent greenhouse gases in the atmosphere to a new record in 2013, while oceans, which absorb the emissions, have become more acidic than ever, the U.N. said on Tuesday.

"We know without any doubt that our climate is changing and our weather is becoming more extreme due to human activities such as the burning of fossil fuels," said Michel Jarraud, the head of the World Meteorological Organization (WMO) that released a report on the issue on Tuesday.