WASHINGTON - Thanks to the high prices of oil and natural gas, the electricity industry is turning back to coal, America's oldest and most abundant fossil fuel, to drive a new generation of power plants. The upshot is that even as politicians take the threat of global warming more seriously, the problem may get much worse. Utilities are proposing to build 154 coal-fired power plants in the next 25 years, according to "Coal's Resurgence in Electric Power Generation," a recent Department of Energy report. Most of those new plants would use conventional coal-burning technology, which would increase carbon dioxide emissions from U.S. coal plants by more than 50 percent by 2030, according to the Energy Information Administration, the analytic division of the Energy Department. A traditional coal plant produces three to four times more CO2 -- a potent "greenhouse gas" that traps the sun's heat and helps raise the Earth's temperature -- than comes from a modern plant that uses natural gas as its fuel.