China issues highest pollution warning for a year... as Xi Jinping meets Barack Obama at the Paris climate change talks

'This sort of weather, you can see that all of Beijing has been completely enveloped in smog'

High-rise buildings are seen during a heavily polluted day in Beijing (Reuters)

Chinese President Xi Jinping has met with US President Barack Obama at the start of two weeks of talks where world leaders hope to reach a new agreement on climate change.

But as the Paris Climate Change Conference commences, Beijing is continuing to encourage its residents to stay indoors to protect themselves from the choking smog which has covered the Chinese capital since Friday.

The highest pollution warning issued so far this year - the 'orange' alert which is the second highest of four levels - was maintained on Monday morning after the Beijing Real-time Air Quality Index (AQI) showed tiny particles of PM 2.5 reached more than 600 micrograms per cubic metre, which is classed as “hazardous”. The government encourages residents to stay indoors if the level exceeds 300.

According to the World Health Organization, 25 micrograms per cubic meter is considered the safe level.

China produces around 30 per cent of the world's greenhouse gases. Coal-powered heating systems used during cold winters are partly to blame for the soaring pollution levels and the thick grey smog.

The number of cities to be affected by “hazardous” levels reached 23 – encompassing 530,000 square km, which is roughly the size of Spain. Air pollution is much worse in the northeast of China where there are many heavy industries including coal mining.

The pollution level has resulted in the closure of highways and the suspension of construction by the Beijing Environmental Protection Bureau. Factories were also asked to limit or suspend their output.

The Ministry of Environmental Protection said the “unfavourable” weather of low wind speeds had been unable to disperse the polluted air. But it is hoped the situation will improve on Wednesday when a cold front is expected.

One of China’s key pledges to reduce its greenhouse gas emissions by 2030 is to reduce its coal consumption.

Zhang Heng, a 26-year-old architect from Beijing, said: “This sort of weather, you can see that all of Beijing has been completely enveloped in smog… and for every breath, getting up every morning, your throat will feel particularly uncomfortable.”

Additional reporting by Reuters