Weekend rain washed away the dangerous pollution that has afflicted Rome in recent weeks but left city authorities with a new headache: roads and pavements made treacherous by bird droppings.

The downpours that cleaned up the air and brought levels of fine particles back down below a World Health Organization-recommended threshold also cleansed the city's trees of several weeks worth of guano deposited by millions of migratory starlings.

More than a million private cars were banned from New Delhi's roads on Friday, as authorities began trialing drastic new measures to cut smog in the world's most polluted capital.

From January 1 only cars with odd-numbered license plates will be allowed on the roads on odd-numbered dates and those with even-numbered plates on the other days to try to reduce pollutant levels which regularly hit 10 times the World Health Organization safe limits.

Temperatures at the North Pole rose above freezing point Wednesday, 20 degrees Celsius above the mid-winter norm and the latest abnormality in a season of extreme weather events.

Canadian weather authorities blamed the temperature spike on the freak depression which has already brought record Christmas temperatures to North America and lashed Britain with winds and floods. 

A revolutionary floating dam that traps plastic bags, bottles and other waste choking the world's oceans will be tested at sea for the first time in 2016, the Ocean Cleanup foundation said.

"It will be the first time our barrier design will be put to the test in open waters," the foundation said of the 100 meter-long (62 miles)  barrier segment that will be deployed 23 kilometers off the coast of The Netherlands in the second quarter of the year.

More than two weeks of heavy pollution led Iranian officials to ban all outdoor sport and impose new traffic restrictions Wednesday as persistent cold weather exacerbated Tehran's air quality problems.

In the worst concerted period of pollution for three years, primary schools and nurseries were closed and new car exclusion zones imposed in the capital.

Millions of Delhi residents will have to find alternative ways to work from Friday, when authorities launch a trial of draconian traffic restrictions to try to clean up the world's most polluted capital.

Private cars will be banned from the roads on alternate days from January 1 as part of a slew of measures aimed at reducing smog levels that include shutting some coal-fired power plants and vacuuming roads to reduce dust.

As many as 58 million large trees in California are threatened by record drought afflicting the state since 2011, says a study published Monday.

Even if the weather phenomenon called El Nino produces more precipitation, California's forests could suffer irreversible change, the report said.

It's every cyclist's dream: no red lights, no trucks, just a clear, smooth lane to zoom down with the wind in your face. Welcome to Germany's first bicycle Autobahn.

Fans hail the smooth new velo routes as the answer to urban traffic jams and air pollution, and a way to safely get nine-to-fivers outdoors.

Swedish courts on Monday ordered a temporary ban on wolf hunting in parts of the country, favoring animal rights activists in one of Sweden's most hotly disputed environmental issues.

The administrative court decisions in the western city of Karlstad, and in Falun, in central Sweden, were a victory for environmental groups including the Swedish World Wildlife Federation, which has been fighting a decision to authorize the culling of 46 wolves. 

Russia is warming more than twice as fast as the rest of the world, the environment ministry said Friday, sounding an alarm on the rise in floods and wildfires nationwide.

A government report on environmental protection  said temperatures in Russia had warmed by 0.42 degrees Celsius per decade since 1976, or 2.5 times higher than the global warming trend of 0.17 degrees.