Human activities are pushing Earth toward a "tipping point" that could cause sudden, irreversible changes in relatively stable conditions that have allowed civilization to flourish, a new study warns. There are signs that a toxic brew of climate change, habitat loss and population growth is dramatically reshaping life on Earth, an international team of researchers reported yesterday in the journal Nature. Go to story #1

PITTSBURGH -- The next big hurdle to bringing renewable energy into the U.S. energy mainstream is being scaled in a nondescript warehouse in this city's gritty Lawrenceville neighborhood, just up the Allegheny River from downtown's high-rise monuments to the bygone era of steel. That's where technology startup Aquion Energy Inc. is preparing to launch production of a new sodium-ion hybrid battery that the company's founders believe will be a game-changer for renewable and off-grid energy resources like solar and wind power. Go to story #2