Associated Press: A new study published Sunday by the journal Nature Climate Change concludes the much-debated Keystone XL pipeline could produce four times more global warming pollution than the State Department calculated this year.
The proposed pipeline would carry oil from tar sands in western Canada to Texas, passing through western Nebraska.
Researchers estimate it would increase world carbon by as much as 121 million tons a year compared with the department's estimate of 30 million tons. Study lead author...