The unexpected energy revolution caused by the rapid growth in North American shale gas production has produced benefits related to the economy, jobs, energy security, and local air pollution, and has contributed to a decrease in US greenhouse gas emissions. However, as my colleagues and I report in a new study published online today by Nature Advance Online Publication (fee required), its overall impact on global greenhouse gas emissions appears to be surprisingly small. In fact, we find that even a very significant expansion in the availability of less-expensive natural gas (up to 300 percent) would have little effect on growing global greenhouse gas emissions.
Because abundant, lower-cost gas is displacing coal in electricity production (where it emits 50 percent less carbon dioxide than coal to produce the same amount of energy), many believed that the recent US natural gas boom could help slow climate change. However, according to our study, globally more-abundant, competitively priced natural gas would displace all energy sources—including both higher-emitting coal and lower-emitting (and relatively more expensive) nuclear and renewable energy technologies, such as wind and solar. In additon, decreasing energy costs accelerates economic growth and increases energy use.
The decision to consider this issue began last year when a group of scientists, engineers, and policy experts, led by Pacific Northwest National Laboratory's Joint Global Change Research Institute (JGCRI), gathered at a workshop in Cambridge, Maryland to consider the long-term impact of a potential major expansion in the availability of affordable natural gas throughout the world. Based on discussions at the workshop, many of us concluded that it would be interesting and valuable to look more closely at possible outcomes. Integrated assessment modeling (IAM) groups from the United States, Australia, Austria, Germany, and Italy formed a collaboration to consider what the world would be like in 2050 with and without a major expansion in the availability of less-expensive natural gas.
As a technical matter, for the study, we adjusted the global supply curve for natural gas to increase the amount of energy that could be produced at less than $3 per gigajoule from 10,000 to over 30,000 exajoules (EJ). These quantities correspond to increasing the amounts of CO2 (carbon dioxide) that would be produced from combustion of natural gas from about 500 to over 1,500 Gigatonnes. Also, note that global use of natural gas amounted to about 100 EJ in the year 2005.
IAM quantitatively represents the varied ways that energy and technology interact to power the economy. Each of the five models provides an integrated, comprehensive representation of the economy and emissions that affect the climate. We show that incorporating the behavior of the entire economy and how people create and use energy from all sources affects emissions in several ways:
- When it replaces coal, natural gas does reduce carbon emissions. However, gas also displaces some more-expensive, low-carbon sources, such as renewables and nuclear energy. Overall changes result in only a small reduction in emissions—nowhere near as large as would occur if gas only replaced coal.
- Abundant, less-expensive natural gas lowers energy prices, which leads people to use more. Lower-cost energy stimulates the economy, which also increases overall energy use.
- Enhanced use of natural gas also leads to leakage of “fugitive” methane, a powerful greenhouse gas, during production and distribution. Although this adds to overall methane emissions, even at the highest rates cited in the literature, leakage does not alter the fundamental picture.
In combination, the models find that the global energy system could experience unprecedented changes in natural gas use (with significant affects on energy use in several sectors), but only slight changes to CO2 emissions and climate forcing. The models project natural gas consumption to increase by up to 170 percent by 2050. Penetration of gas is greatest in the power sector and minimal in transportation. However, changes in global CO2 emissions are much smaller: ranging from a 2 percent reduction to an 11 percent increase. Related changes to total radiative forcing of climate range from -0.3 percent to +7 percent.
These results are similar to those in several recent studies for the United States alone. The Nature article broadens the analysis in two important ways: 1) it considers the entire globe through 2050, and 2) it presents results from five different integrated assessment models, each with a different modeling structure, that reinforce the primary conclusions.
Finally, it is important to highlight two points. First, our Nature paper considers a world acting under market forces with no additional policies. Work in progress by the team aims to extend the analyses to consider the implication of additional policies (for example, to limit greenhouse gas emissions, promote renewable energy, restrict coal, or to promote or inhibit nuclear). Second, results derive from complex but idealized economic models with explicit representations—of future technologies, for example—that cannot foresee all possibilities. For instance, a significant expansion of natural gas distribution and use could catalyze new, currently unforeseen combinations of technologies, such as for storage and use of energy, with important consequences for efficiency and emissions. A summary of last year’s Global Technology Strategy Program: Abundant Gas Workshop, Global, Long-Term Implications of Abundant Natural Gas, provides some discussion of both these points and others. The preliminary scenario produced by JGCRI and discussed at the workshop differs slightly from that used in our Nature paper.
