With global warming, so much is resting on faith

However, critics say the government effort is too slow and needs refocusing.

A review by the Energy Department's research lab said the program focused too much on work that can lead to "only incremental improvements" and called for emphasis on "exploratory, out-of-the-box concepts."

A new government economic analysis recommends paying attention to markets in combination with research.

The Congressional Budget Office report said any cost-effective US policy on global warming must put a price on carbon -- via an emissions tax or a "cap and trade" system of buying and selling emissions allowances among companies, as in Europe.