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 kw...@wvgazette.com or 304-348-1702.