Air conditioners powered by waste heat from place like electrical plants.
It's time to face the facts. The US spot at number 1 is coming to an end.
What's in and what's out this year in global news?
Swimmers break the ice and brave freezing waters for a "refreshing" dip.
As it struggles to overcome its 1994 genocide, Rwanda is dynamic and compelling.
Santa goes extreme around the world, from skydiving to swimming with whales.
It's been an historic year. Here are our favorite photos from 2011.
As they forge a fiscal union, euro zone leaders blame UK departure on shameless self-interest.
Pearl Harbor, images from a day of "infamy."