UN Secretary-General Ban Ki-moon told a meeting of business leaders in Copenhagen that "climate change is the defining challenge of our time."

From a design award-winner to a model that uses the updraft on a roof, small residential wind turbines are getting smarter and sexier.

Wisconsin's landmark out-of-basin diversion of the Great Lakes is getting both praised and blasted by water watchers.

The Indianapolis Speedway, site of yesterdays Indy 500, mounts a major effort to be environmentally friendly.

The push for greener cars will likely bring a boom for companies that mine and refine lithium -- a key ingredient in batteries.

"Rows of tall turbines have already remade the landscape on wheat farms and ridgelines on private land around the region. But so far there have been no wind farms built on public land in the Northwest. That's about to change."

"It's an old energy problem with a new solution: After decades of facing prohibitively high costs to install solar panels, Massachusetts residents will be able to lease the panels for a tiny fraction of their upfront cost."

Zebra mussels, which have caused an estimated $5 billion in damage to the Great Lakes, have been found in a Maryland tributary of Chesapeake Bay. If they spread, they could threaten the less-salty waters of the Bay.

"OSLO -- A rise in concentrations of a powerful greenhouse gas over the Arctic after a decade of stability is stirring worries about a possible thaw of vast stores trapped in permafrost, experts said."

U.N. Secretary-General Ban Ki-moon said the climate bill approved Thursday by the House Energy Committee is 'not enough' to stem warming to the degree hoped for in the next climate treaty.