CHARLESTON, W.Va. -- Earlier this month, when business boosters, community organizers and labor advocates gathered to brainstorm about diversifying the economy in West Virginia's coalfields, one alternative was mentioned over and over: The boom in natural gas production in the Marcellus Shale region of the state. Over the past decade, West Virginia's natural gas production has more than doubled. Jobs in the industry have jumped by 55 percent. The natural gas boom here and across the nation has brought climate change benefits. The continuing switch by power plant owners from coal to natural gas -- along with dramatic increases in renewable power generation -- has helped reduce carbon dioxide emissions from the U.S. electricity sector to their lowest levels since 1994. West Virginia political leaders tout natural gas as the state's energy and economic future. They say the jobs will keep coming, and that spin-off businesses from natural gas production will eventually revitalize the state's chemical-making industry. President Obama is targeting greenhouse emissions from coal-fired power plants as part of his plan to combat climate change. The administration has warmly embraced the natural gas boom, citing the switch from coal to gas for electricity generation as one way to combat climate change. However, despite some recent hopeful study results, questions continue about global warming pollution from natural gas. Some recent studies emphasize that gas might not be the best long-term climate solution. As with coal, experts say any desire to continue using natural gas long into the future needs to include plans to widely deploy carbon capture and storage, or CCS, technology on power plants. For now, West Virginia leaders may focus on natural gas as an economic savior but, before too long, they might have to face the same questions about the industry's greenhouse emissions as they are now confronting about coal. In one new report, the Union of Concerned Scientists warned that continued increases in the use of natural gas for electricity generation too far into the future carries with it the risk of the worst consequences of climate change. "An electricity future with greater use of natural gas and increasing carbon emissions is clearly the wrong path for the United Sates," Steve Clemmer, director of energy research for UCS, wrote in explaining his group's report. On Friday, the world's scientists issued their latest report summarizing the state of knowledge about global warming. In its fifth assessment of the science, the Intergovernmental Panel on Climate Change said warming of the planet is "unequivocal." The atmosphere and oceans have warmed, the group said. Snow and ice have diminished, the sea levels have risen and the concentration of greenhouse gases continues to increase. The IPCC said it is "extremely likely" -- scientists are 95 percent or more certain -- that "human influence has been the dominant cause of the observed warming since the mid-20th century." "Continued emissions of greenhouse gases will cause further warming and changes in all components of the climate system," the IPCC said in a 36-page summary report for policymakers. "Limiting climate change will require substantial and sustained reductions of greenhouse gas emissions." For years, the conventional wisdom was that natural gas was a good alternative to coal, producing half the carbon dioxide emissions per unit of energy when burned in a power plant. However, natural gas itself is mostly methane, a powerful greenhouse gas, and the conventional thinking didn't take into account methane emissions during the process of drilling for, producing and transporting natural gas. Two years ago, the issue gained much more attention with the publication of a study by a team of Cornell University researchers, led by ecology professor Robert Howarth. That study reported that natural gas could be just as bad -- or worse -- than coal for global warming, especially if the issue is examined on the short time frame in which scientists believe action is needed to curb global warming. Since then, industry officials have harshly criticized Howarth's study, and there's been a lively debate in scientific journals about his results and about the many variables used to estimate methane emissions from the shale-gas boom across the country. Two weeks ago, a University of Texas study reported actual emissions measurements that suggested methane emissions from the natural gas industry were less of a concern. Even some of the harshest natural gas critics saw the findings as potentially good news, but they noted that the study covered only a small share of potential emissions points, focused on industry-picked production sites, and had a variety of other shortcoming. In its recent report, the Union of Concerned Scientists tried to estimate the impact of various energy mixes on atmospheric concentrations of greenhouse gases. The UCS examined four recent analyses by government and private groups that reviewed the potential effects on the nation's electricity sector of different sorts of energy pathways. Each of the studies found that, under current law and regulations, natural gas generation would continue to grow over the next few decades, as much as tripling by 2050, to keep up with increasing electricity demand. "Moreover, these four studies show that greater use of natural gas for generating electricity could contribute to that sector's overall increase in carbon dioxide emissions," said the UCS report, called, "Gas Ceiling: Assessing the Climate Risks of an Over-reliance on Natural Gas for Electricity." "Because of the continued dominance of fossil fuels and rising demand, emissions through 2050 would be 5 [percent] to 25 percent higher than today's levels," the report said. The U.S. Energy Information Administration similarly projects that electricity-related carbon dioxide emissions would rise 12 percent above 2012 levels by 2040. At the same time, the National Research Council has said, to avoid the worst climate change impacts, power sector carbon dioxide emissions need to be cut by 90 percent from current levels by 2050. Most of the reductions are needed early on, during next 20 years, the council has said. One scenario modeled by the UCS shows natural gas generation increasing significantly through 2025, continuing to replace coal plants, but then steadily declining through 2050. "While natural gas can play an intermediate role in temporarily replacing some of the decline in coal generation, its use must be scaled back considerably over the long term in order to meet climate goals," the UCS report said. Theh UCS said another scenario it modeled would rely more on renewable energy, such as wind and solar, and on energy efficiency improvements. "In addition to relying less on natural gas, the renewables and efficiency pathway has the lowest cost," the report said. "Under this pathway, consumer electricity bills by 2050 are one-third lower . . . as reductions in electricity use from energy efficiency more than offset the costs of investing in renewable energy technologies." By contrast, the UCS report said, using more nuclear power and CCS technology is the most expensive route, resulting in a 20-percent increase in consumer electricity bills by 2050. Reach Ken Ward Jr. at email@example.com or 304-348-1702.