President Obama (from left), French President Francois Hollande and Microsoft co-founder Bill Gates applaud a speech during the Mission Innovation event at the UN conference on climate change Monday in Paris.
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A building called Sustainability Base, at NASA's Ames Research Center in Mountain View, Calif., has an energy-efficient design that allows in sunlight. So for most of the year, the interior is illuminated by natural light.
A power-generating windmill turbine is seen in front of the Arc de Triomphe on the Champs Elysees avenue in Paris ahead of the COP21 World Climate Summit, which begins Monday.
Christian Hartmann/Reuters /Landov
President Obama (center) and Secretary of State John Kerry (right) attend Monday's opening ceremony of the United Nations Climate Change Conference in the Paris suburb of Le Bourget.
Delegates from about 170 countries gathered in Kyoto in December 1997 during the United Nations Framework Convention on Climate Change. This year in Paris, the stakes are even higher, negotiators say.
Oranges ripen in a grove in Plant City, Fla. Citrus greening, a disease spread by a tiny insect that ruins oranges and eventually kills the trees, has put the future of the state's $10 billion citrus industry in doubt.
Coal fires burn early in the morning in January 2014 at a privately owned coal mine in India's Jharkand state, making the air dense with noxious smoke and dust. Forty percent of India's mineral wealth lies in Jharkhand.