Using plentiful and inexpensive natural gas alone won't slow the growth of global greenhouse gas (GHG) emissions over the long-term and may in fact contribute to it, according to an analysis by a team of scientists and researchers who worked with the U.S. Department of Energy's Pacific Northwest National Laboratory (PNNL).
Natural gas emits half the carbon dioxide (CO2) of coal, and many scientists have thought that recent gains in gas supplies would help to slow climate change as consumers and manufacturers switched from coal to gas. In fact, increased natural gas use was considered to be at least partially responsible for a decline in U.S. CO2 emissions between 2007 and 2012.
However, abundant stores of inexpensive natural gas eventually would compete with all types of energy sources -- not just higher-emitting coal, but also lower-emitting nuclear and renewable energy technologies, according to PNNL's study published on Wednesday in Nature. Cheap gas in turn would accelerate economic growth and expand overall energy consumption.
"The effect is that abundant natural gas alone will do little to slow climate change," said lead author and PNNL economist Haewon McJeon. "Global deployment of advanced natural gas production technology could double or triple the global natural gas production by 2050, but greenhouse gas emissions will continue to grow in the absence of climate policies that promote lower carbon energy sources."
Advances in gas production technology based on horizontal drilling/hydraulic fracturing have produced a bounty of low-cost gas for North America, and many renowned government and private researchers have linked the boom to GHG reductions. Whether the advanced technologies could impact emissions beyond North America and into the future was a question that researchers wanted to answer in the new study.
A group of scientists, engineers and policy experts led by PNNL's Joint Global Change Research Institute met in Cambridge, MD last year to consider the long-term impact of expanding the current gas boom on the world. The researchers, divided into five teams, projected what the world could be like in 2050 with and without a global gas expansion. They used different computer models that had been independently developed to account for energy use, the economy and climate, as well as the way the systems interacted with one another.
"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 PNNL's chief scientist James "Jae" Edmonds. "When we saw all five modeling teams reporting little difference in climate change, we knew we were onto something."
What the researchers discovered through the various models was:
Gas replacing coal reduces carbon emissions, but it also replaces some low-carbon energy sources such as renewables or nuclear energy, which results in a smaller reduction than expected because natural gas becomes a bigger part of the energy supply.
Less expensive gas would lower energy prices across the board, leading people to use more energy overall, thereby stimulating the economy and thus increasing overall energy use. Consequently, the energy consumption grows.
The main component of gas, methane, is a more potent GHG than CO2. During production and distribution, some methane leaks, and even at the lower end, fugitive methane emissions would add 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," the research found.
"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.
PNNL researchers were supported by the Global Technology Strategy project, a public-private partnership. Scientists, engineers and economists who also contributed to the research represented the University of Maryland, BAEconomics, the International Institute for Applied Systems Analysis, the Potsdam Institute for Climate Impact Research, the Centro Euromediterraneo sui Cambiamenti Climatici and Resources for the Future.