US top scientists urge coal, oil use penalties

WASHINGTON (AP) - The nation's top scientists say global warming is so urgent that the United States must make it more expensive to use coal and oil.

The National Academy of Sciences, an advisory panel to the government, is taking the unusual step of urging specific actions to curb global warming. Normally, the academy speaks out on scientific matters but doesn't recommend policy.

The academy says the nation needs to cut its greenhouse gas emissions from 57 to 83 percent by 2050. That's about what President Barack Obama has called for. The academy says the way to do that is through a carbon tax or a cap-and-trade system that would limit pollution from carbon dioxide, a major contributor to global warming.