Right now, there are 28 mega-cities in the world, with about 450 million inhabitants among them. So, which world cities make the cut?
A recent documentary, "Under the Dome," depicts Chinese residents coping with worsening air quality. Just how bad is pollution in China?
The controversy over construction of Nicaragua's Interoceanic Grand Canal makes it a good time to look at the some of the biggest man-made waterways on the planet.
The removal of the documentary underscores the ruling Communist Party's sensitivity to public debate over China's notorious smog problem.
See images from the 2015 Harbin International Ice and Snow Festival, home of the world's largest ice sculptures.
Air pollution in Beijing dropped about 4 percent last year, though levels of dangerous particulate matter remained more than three times the recommended limit.
Negotiators will meet to thrash out details of the next global climate pact, which is already shaping up as an improvement on the Kyoto Protocol. Continue reading →
Will the recent agreement struck between the United States and China on greenhouse gas emissions really help matters or will it all be so much hot air? Trace examines the deal and what could come from it.
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