GOLDEN, COLO. -- Here in Coors country, the first casualty of a war against global warming could be the price of a cold beer.

Most plans to prevent the planet from overheating feature hefty taxes on the source of warming gases: fossil fuels such as coal and oil used extensively by Adolph Coors Co. to fire brew kettles and run its trucks. "Those {tax} dollars would be pretty hard to absorb," said Bob Mooney, the brewery's energy manager. "It would be a significant pass-on to the consumer."

But 150 miles southwest of here, at the Rocky Mountain Institute, the warming threat is seen as an impetus for savings, not a source of higher costs. To prove his point, Amory Lovins heats his 4,000-square-foot energy research institute without a furnace on sub-zero days and runs heavy office machines, appliances and lights on an electric bill that averages less than $50 a month.

Such contrasting views of a future without cheap fossil fuels transcend the Colorado Rockies to the highest councils of government worldwide, explaining why different nations have different goals for the U.N.-sponsored negotiations on global warming opening in the Washington area today.

The Intergovernmental Negotiating Committee on a Framework Convention on Climate Change has blocked out the next two years to reach an agreement. Whether the 130 participating nations simply strike a consensus on the seriousness of the threat of global warming or agree on concrete measures to combat it will depend largely on how negotiators compute the implications for their economies.

Until recently, the only estimates were on the costs of global warming -- caused by the buildup of heat-trapping gases. The 2- to 6-degree increase in average temperature predicted by some scientists for the next century could wither crops and raise sea levels and inundate coastal towns.

As governments search for solutions to global warming, the investigations of the costs of those remedies have picked up speed.

Forecasts for the U.S. economy vary. Different economists predict a 21st century of staggering energy prices and much higher costs for manufacturers like Coors -- or alternatively, an energy-efficient future such as that envisioned by Lovins in which power plants and gas pumps close for lack of need.

The Bush administration is wed to the gloomiest economic predictions. Officials say that the general White House view that national income will decline 3 percent as a result of steps to halt global warming will put a stronger brake on U.S. negotiators than the oft-cited reason to postpone action: scientific uncertainties about how much temperatures will rise and how disruptive global warming will be.

Some officials question whether the cure is harsher than the disease; there are estimates that the damage caused by global warming would reduce national income only 0.25 percent a year.

At the center of administration concerns is the fate of fossil fuels -- targeted by European regulators because when burned in engines or industrial plants they produce the principal warming gas, carbon dioxide. The United States is much more dependent on coal and oil than is Europe, which uses far more nuclear power.

Among its major industrial trading partners -- Japan, Europe and Canada -- only the United States has resisted plans to control carbon dioxide. Indeed, U.S. emissions, already a quarter of the world total, are expected to grow 15 percent by the year 2000.

The costs of reversing that growth are the subject of lively debate. Economists have programmed their most sophisticated computers to project the impact on the U.S. economy of plans by some European nations to freeze emissions of carbon dioxide at current levels by the year 2000 and cut them by up to 20 percent in the next few decades.

Everyone agrees that however those goals are reached would require a profound change in U.S. energy consumption. But there are wide differences of opinion over the economic costs of those changes.

Most economists agree that the easiest and fairest way to reduce the use of fossil fuels is to tax their extraction. The higher prices engendered by the fee, based on the carbon content of the fuel, supposedly would discourage consumption. The tax would be raised until it dampened demand for fossil fuel enough to achieve the desired reduction in carbon dioxide emissions.

According to the analysis most influential with White House advisers, a carbon tax of $250 a ton would be needed, which economists Richard Richels and Alan S. Manne estimate would boost gasoline prices 75 cents a gallon and coal prices five-fold. That would double electricity bills.

For Coors, which runs the world's largest brewery here, the prospect of a carbon tax is about as welcome as a return to prohibition. The company burns 400,000 tons a year to operate its brewing process and 1.2 million gallons of oil to run the inner-brewery fleet.

One response might be to buy more natural gas -- Coors already uses 1.75 billion cubic feet a year -- to fire its copper brew kettles and huge refrigeration unit, said Coors's Mooney. But the price of natural gas already is twice that of coal, before the carbon tax.

"Any way you cut it, it's going to run up the dollars," Mooney said of the carbon tax.

Manne and Richels believe that higher energy prices resulting from a carbon tax will reduce national production 1 to 5 percent annually, depending on the extent of energy conservation and availability of low-cost alternatives.

"If we're thinking about reducing carbon dioxide emissions today to prevent some damage in the future, the insurance premium will not be inexpensive," said Richels, an energy modeler at Electric Power Research Institute, funded by utilities.

"Until we have a better handle on what's at stake from an environmental damage perspective, its going to be difficult to say whether the benefits {of carbon dioxide controls} justify the cost," he said.

Many consider the analysis of Manne and Richels extreme because it assumes rising energy costs will only mildly diminish consumption, requiring a more onerous tax than other economists believe necessary.

According to a group of Harvard economists, for example, rising energy costs would quickly dampen consumption and spur use of fossil fuel alternatives. They estimate that carbon taxes as low as $45 a ton would achieve a 20 percent cut in carbon dioxide emissions.

Another flashpoint in the debate is the potential for improvement in U.S. energy efficiency. Manne and Richels assume it is very limited in the long run.

But Robert H. Williams, an analyst at Princeton University's Center for Energy and Environmental Studies, believes carbon taxes would quicken the development of a "new regime" of low-cost energy sources -- such as wind and solar -- with such promise for savings that there would be a net economic gain.

If the rate of improvements in energy efficiency meet Williams's expectations -- which is three times faster than Manne and Richels assume -- U.S. demand for energy would drop by two-thirds over the next 100 years, he said.

There likely is no better illustration of the potential of energy efficiency than Lovins's institute in Snowmass, Colo. Known locally as the "solar castle," the building actually benefits from the "greenhouse effect" by drawing the sun's heat into a large, glass-enclosed room and then distributing it through a system of fans and ducts.

Its energy-saving devices -- from compact fluorescent lamps to triple-pane windows and rooftop solar panels -- cost $6,000 to install in 1983 and save an estimated $7,100 a year in electricity and heating costs.

According to Lovins, the building demonstrates the vast savings possible were fossil fuels replaced with a little common sense. New technologies for lighting, motors, pumps and car engines are available and have only to be advertised to cut dramatically the nation's need for and cost of energy.

"The carbon dioxide and other pollution avoided by substituting efficiency for fuel is thus avoided not at a cost but at a profit," Lovins said.