Natural gas expansion not enough to slow climate change

In a new study, scientists have found that natural gas alone was not enough to slow the growth of global greenhouse gas emissions worldwide.

Because natural gas emits half the carbon dioxide of coal, many people hoped the recent natural gas boom could help slow climate change, and according to government analyses, natural gas did contribute partially to a decline in U.S. carbon dioxide emissions between 2007 and 2012. But, in the long run, according to this study, a global abundance of inexpensive natural gas would compete with all energy sources - not just higher-emitting coal, but also lower-emitting nuclear and renewable energy technologies such as wind and solar. Inexpensive natural gas would also accelerate economic growth and expand overall energy use.

Lead author Haewon McJeon said that global deployment of advanced natural gas production technology could double or triple the global natural gas production by 2050, but greenhouse gas emissions would continue to grow in the absence of climate policies that promote lower carbon energy sources.

A group of scientists, engineers and policy experts, led by PNNL's Joint Global Change Research Institute, gathered at a workshop in Cambridge, Maryland, in April 2013 to consider the long-term impact of an expansion of the current natural gas boom on the rest of the world. The researchers, hailing from the U.S., Australia, Austria, Germany and Italy, went home and projected what the world would be like in 2050 with and without a global natural gas boom. The five teams used different computer models that had been independently developed.

Their computer models included not just energy use and production, but also the broader economy and the climate system. These "integrated assessment models" accounted for energy use, the economy, and climate and the way these different systems interact with one another. The groups each computed projections halfway into the century.

The key, the researchers said, was that the five different models provide an integrated, comprehensive view of the economy and the Earth system. Swapping out coal for natural gas in a simple model would cut greenhouse gas emissions, a result many people expected to see. But incorporating the behavior of the entire economy and how people create and use energy from all sources affect emissions in several ways:

Natural gas replacing coal would reduce carbon emissions. But due to its lower cost, natural gas would also replace some low-carbon energy, such as renewable or nuclear energy. Overall changes result in a smaller reduction than expected due to natural gas replacing these other, low-carbon sources. In a sense, natural gas would become a larger slice of the energy pie.

Abundant, less expensive natural gas would lower energy prices across the board, leading people to use more energy overall. In addition, inexpensive energy stimulates the economy, which also increases overall energy use. Consequently, the entire energy pie gets bigger.

The main component of natural gas, methane, is a more potent greenhouse gas than carbon dioxide. During production and distribution, some methane inevitably escapes into the atmosphere. The researchers considered both high and low estimates for this so-called fugitive methane. Even at the lower end, fugitive methane adds to climate change.

The combined effect of the three, the scientists found, was that the global energy system could experience unprecedented changes in the growth of natural gas production and significant changes to the types of energy used, but without much reduction to projected climate change if new mitigation policies were not put in place to support the deployment of renewable energy technologies.

The study is published in Nature.