Powerstation
The Energy Department says the amount of carbon dioxide released into the atmosphere in the U.S. the first part of this year was the lowest it's been in 20 years. - 

This final note today. A hint of optimism about climate change. The Energy Department says the amount of carbon dioxide released into the atmosphere in the U.S. the first part of this year was the lowest it's been in 20 years.

How come? Near as anyone can tell, it's because natural gas has gotten so much cheaper than coal.

'Course, there is no such thing as a free lunch. Gas is cheaper because there's so much hydraulic fracturing -- fracking -- going on...which is a whole different set of problems.

Follow Kai Ryssdal at @kairyssdal