Top executives at many utility companies have reluctantly accepted that coal-fired power plants contribute to global warming, and they have begun planning for a more restrictive future. Then there is C. John Wilder, chief executive of TXU Corp...[which] is racing to build 11 big power plants in Texas that will...[release] substantial amounts of carbon dioxide...Critics of its $11 billion construction program see...[the following] motivation: The federal government may slap limits on carbon-dioxide emissions. If it does, plants completed sooner may have a distinct advantage. That's because the government may dole out "allowances" to release carbon dioxide, and plants up and running when regulations go into effect may qualify for more of them than those built at a later date. TXU opposes such regulations... Other big utility companies, including American Electric Power Co., Xcel Energy Inc. and Duke Energy, have proposed newer-style plants that release fewer pollutants and make it easier to control carbon-dioxide emissions... TXU says it has already reduced carbon-dioxide emissions per unit of electricity produced by adding wind turbines and nuclear power to its mix... J. Wayne Leonard, chief executive officer of Entergy Corp.,...says the science behind global warming is persuasive and carbon-dioxide regulation is inevitable and necessary. He calls it "unacceptable" for power companies to build lots of new plants heedless of the environmental effect of carbon dioxide... Bechtel Corp. and General Electric Co. are working together to design a gasification power plant [with lower emissions] that would cost about as much to build as the [higher-emission] type of plant that TXU intends to build... Some companies think allowances should be doled out in a way that rewards companies for early, voluntary reductions. In 2002 the state of California created an organization called the California Climate Action Registry to document and verify reductions of several greenhouse gases by companies and public agencies...to secure credit for companies that take early action. Energy producers such as PG&E Corp., Mirant Corp., BP PLC and the Los Angeles Department of Water and Power are participants.