Half of Beijing's private cars were ordered off the streets Tuesday and many construction sites and schools were closed under the Chinese capital's first-ever red alert for pollution.

A grey haze descended on the city of around 21.5 million people, with levels of PM2.5 -- harmful microscopic particles that penetrate deep into the lungs -- at one point above 300 micrograms per cubic metre according to the U.S. embassy, which issues independent readings.

U.S. Secretary of State John Kerry arrived in Paris on Monday for the final intense days of negotiation at a U.N. conference seeking a landmark pact on climate change.

Senior U.S. officials said Washington was cautiously optimistic the talks, scheduled to end on Friday, would unlock an ambitious deal to lower carbon emissions and combat the impact of global warming.

Time is running out to avert "a climate catastrophe," U.N. chief Ban Ki-moon warned Monday as ministers opened a frenetic week of talks in Paris to forge a 195-nation accord to brake global warming.

Scientists predict Earth will become increasingly hostile for mankind as it warms, with disastrous storms, floods and droughts, and rising sea levels that will consume islands and eat away at populated coasts.

China's capital issued its first ever red alert for pollution on Monday, as a new blanket of choking smog was projected to descend on the city.

From Tuesday morning, half of Beijing's private cars will be ordered off the road, with an odd-even number plate system in force, and 30 percent of government vehicles also garaged.

A coalition of African countries and donors unveiled an ambitious initiative on the sidelines of a crunch U.N. climate conference Sunday to restore 100 million hectares (250 million acres) of degraded and deforested land by 2030.

Called the African Restoration Initiative (AFR100), the project aims nurturing forest regrowth that becomes a powerful "carbon sink," absorbing climate-altering carbon dioxide, and provides a livelihood for the rural poor.

Pope Francis on Sunday urged nations to act with "courage", the day before U.N. talks aimed at saving mankind from the dire impacts of global warming enter their crunch phase.

Ministers begin a frenetic week of negotiations Monday to seal a historic 195-nation agreement in Paris.

Ultra-light, fast and cheap: more than a century after the Wright brothers flew the world's first powered aircraft, a small Slovenian company now hopes to revolutionize the aviation industry with its award-winning electric planes.

Pipistrel's pioneering Taurus Electro is seen as a breath of fresh air in a sector responsible for 13 percent of CO2 emissions from all transport sources.

Unlike many of their neighbors living near the banks of the River Thames in southwest England, Martin and Joanna worry little about their charming country home being engulfed by floods.

Wary of the dangers posed by climate change and a history of disastrous flooding in this pretty part of Oxfordshire, an hour's drive from London, the couple have opted for a home built half a meter off the ground on 27 steel pillars.

Nicolas Denieul plants his spade in the ground and turns over a clod of soil to reveal a mass of earthworms seething around plant roots -- fat ones and thin ones, delicate translucent violet and dark brown.

"That is magnificent. Ten years ago, I never thought I'd see anything like that!" said Denieul, a cheerful French farmer, his hands full of earth in the biting wind.

Negotiators from 195 nations will race Saturday to complete a four-year mission by delivering a blueprint to secure humanity from the consequences of rampant emissions of climate-altering greenhouse gases.

Despite being riddled with conflicting proposals, the draft to be submitted by lunchtime will form the skeleton of the most complex and consequential global accord ever attempted.