Beach trash? A poor catch in a fishing net? Take a look at the arresting and disturbing images photographic artist Chris Jordan recorded on Midway Atoll in the Pacific Ocean.

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A salty soup of seawater, microscopic pieces of plastic and marine debris. That's the ingredients in the North Pacific Gyre, an ocean vortex estimated by Greenpeace to be the size of Texas. Project Kaisei aims to clean it up.

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In order to stop dangerous climate change we may be forced to construct giant solar shades, cloud-making ships and cover great swathes of land with artificial trees that suck up CO2.

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• Explainer: How does geo-engineering work?
  

While the world remembers the fall of the Berlin Wall 20 years ago, one frontier of the Cold War remains intact; the demilitarized zone that separates North and South Korea. And it's become an accidental paradise for rare wildlife.

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Making a set of subway stairs into a piano and a bottle bank into an arcade game; just two clever ways to get people to take time to do the right thing and have fun.

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