National Geographic: Ready for some good news about the environment? Emissions of carbon dioxide in the United States are declining. But don't celebrate just yet. A major side effect of that cleaner air in the U.S. has been the further darkening of skies over Europe and Asia.
The United States essentially is exporting a share of its greenhouse gas emissions in the form of coal, data show. If the trend continues, the dramatic changes in energy use in the United States-in particular, the switch from coal to newly abundant...