In the northern Indian city of Moradabad fumes from burning electronic waste blend with seasonal smog to create an even deadlier mix of pollutants than in Delhi, where filthy air has caused public outcry and made global headlines.

India's smog crisis has centred on the capital but pollution is as bad or worse beyond its borders, with millions in smaller cities like Moradabad barely aware of the harmful effects of the air they breathe.

Climate change imperils one in four natural World Heritage sites, including coral reefs, glaciers, and wetlands -- nearly double the number from just three years ago, a report said Monday.

Air pollution in New Delhi worsened again Sunday and officials warned of little relief in sight from the smog, which has even caused one airline to cancel flights to the world's most polluted capital.

The world must sharply draw down greenhouse gas emissions and suck billions of tonnes of carbon dioxide from the air if today's youth are to be spared climate cataclysm, a top scientist has warned.

As thick smog crept over India's capital this past week and smudged landmarks from view, Nikunj Pandey could feel his eyes and throat burning.

Pandey stopped doing his regular workouts and said he felt tightness in his lungs. He started wearing a triple layer of pollution masks over his mouth. And he became angry that he couldn't safely breathe the air.

The failure of wealthy nations to deliver on short-term climate commitments could hinder the rollout of a landmark treaty, a bloc of 134 developing countries, including India and China, warned at UN negotiations in Bonn.

How's this for awkward? The United States has a delegation at international climate talks in Bonn that will be telling other nations what they should do on a treaty that the president wants no part of.

President Donald Trump has promised to withdraw the U.S. from the 2015 Paris climate pact where nations set their own goals to reduce the emissions of heat-trapping gases, but because of legal technicalities America can't get out until November of 2020.

Delhi shut all primary schools on Wednesday as pollution hit 70 times the World Health Organization's safe level, prompting doctors in the Indian capital to warn of a public health emergency.

Syria told the U.N. climate talks in Bonn on Tuesday that it would join the Paris Agreement, leaving the United States as the only nation in the world opting to stay outside the landmark treaty.

A public health emergency was declared in New Delhi Tuesday as a choking blanket of smog descended on the world's most polluted capital city.