A boom in global natural gas, by itself, will not slow climate change

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.

Five for five
“We didn’t really know how our first experiment would turn out, but we were surprised how little difference abundant gas made to total greenhouse gas emissions even though it was dramatically changing the global energy system,” said James “Jae” Edmonds, PNNL’s chief scientist at JGCRI. “When we saw all five modeling teams reporting little difference in climate change, we knew we were onto something.”

The key, the researchers said, is 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.

Incorporating the behavior of the entire economy, however, and how people create and use energy from all sources affect emissions in several ways:

• Natural gas replacing coal would reduce carbon emissions. Due to its lower cost, however, 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, is 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 are not put in place to support the deployment of renewable energy technologies.

“Abundant gas may have a lot of benefits — economic growth, local air pollution, energy security, and so on. There’s been some hope that slowing climate change could also be one of its benefits, but that turns out not to be the case,” said McJeon.

— Read more in Haewon McJeon et al., “Limited impact on decadal-scale climate change from increased use of natural gas,” Nature (15 October 2014) (DOI: 10.1038/nature13837)