A surge in natural gas has helped drive down coal burning across the United States and Europe, but it isn't displacing other fossil fuels on a global scale. Instead, booming gas use is fueling the global growth in greenhouse gas emissions, according to a new study by researchers at Stanford University and other institutions.

In fact, natural gas use is growing so fast, its carbon dioxide emissions over the past six years actually eclipsed the decline in emissions from the falling use of coal, the researchers found.

Renewable energy sources such as wind and solar are also failing to cut emissions fast enough, the report says, as much of their growth has provided new energy supplies instead of displacing fossil fuels.

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The findings of the study, published Tuesday, support those from other recent studies that found the world is continuing to rely on fossil fuels—including coal—to meet growing energy demand, even as renewable energy sees soaring growth.

"Globally, most of the new natural gas being used isn't displacing coal, it's providing new energy. That's the key interaction, and that's true for renewables even," said Rob Jackson, a professor of Earth system science at Stanford's School of Earth, Energy & Environmental Sciences and the report's lead author. "We need renewables that displace fossil fuels, not supplement them."

Jackson's paper, published in the scientific journal Environmental Research Letters, is one of three included in Global Carbon Project's annual update on the global carbon budget.

They show that carbon dioxide emissions from fossil fuels are expected to grow by 0.6 percent this year. That would be significantly slower than last year, when emissions grew by 2.1 percent. But it would mark the third straight year of growth, after three years of stable emissions. The assessment does not include the methane emissions released by producing and shipping fossil fuels.

Each year of growth makes it harder and more expensive to meet the goals of the Paris climate agreement of limiting global warming to well below 2 degrees Celsius (3.6°F) from pre-industrial levels.

Supplementing Rather Than Supplanting

Natural gas presents a particular challenge.

In the U.S., coal use has fallen by half over the past 15 years, and the biggest reason for that is the expanded use of natural gas, Jackson said. This year, wind and solar power are responsible for only one-sixth of the drop in coal use. This decline in coal power generation is the main reason U.S. emissions are expected to fall by nearly 2 percent this year, and why they fell by an annual average of nearly 1 percent over the previous six. A similar trend has occurred in Europe, where the decline of coal has, in some cases, been even sharper.

These shifts are also being used by the oil and gas industry and its supporters in government to argue in favor of drilling for more gas, not less. Supporters often refer to natural gas as a "bridge fuel" between higher-emitting fossil fuels and renewable energy, but some industry executives have instead begun calling it a "forever fuel"—one they see continuing to grow for decades to come.

Globally, natural gas is the fastest growing fossil fuel.

One of the biggest developments has been a rapidly expanding market for liquefied natural gas, or LNG, an energy-intensive product that allows energy companies to ship gas overseas. Australia has tripled its LNG exports since 2013, the report says, and is now the largest exporter. The U.S. recently opened five new LNG terminals and has been pushing to expand exports further. Several countries opened new import facilities to buy that gas last year in Asia and the Americas. This booming market is sending down gas prices in many developing countries, driving new demand.

Jackson warned that much of this growth is supplementing coal power generation, rather than supplanting it. In Japan, the vast majority of new gas imports since 2010 have replaced nuclear capacity lost after the accident at Fukushima, for example.

Another concern is that all of this new infrastructure—an LNG terminal can cost billions of dollars to build—will make it far more difficult to cut emissions years from now, when investors will be expecting returns from these projects.

"I have strong concerns about the pace of our natural gas build-out in the United States and globally," Jackson said, "because those facilities will be producing pollution for many decades."

Oil, Cars and China's Coal Problem

Coal has continued to hang on in China, India and much of the developing world. This year, the report says, coal use is expected to increase by nearly 1 percent in China, helping drive the country's emissions growth of about 2.6 percent.

China now accounts for half of global coal consumption, and a recent report by the Global Energy Monitor found that the country has plans to build a slate of new coal plants that would match the capacity of all the coal power generation of the European Union.

A separate report, by BNEF, found that coal power generation in developing nations reached a new high in 2018. The report also found a decline in new investment in clean energy.

When it comes to oil, even the slight decline in use in the U.S. expected this year won't be enough to counter growth in China, India and the developing world, Jackson's study found. Most troubling, he said: There's little indication that growth in oil use will end soon.

Americans consume 16 times more oil than people in India, and six times more than those in China, and both nations are set for huge increases in vehicle use. In China, the number of cars has quadrupled since 2007, and the vast majority are fueled by oil. While Chinese people bought 1.1 million new electric cars last year, or more than half the global market, they also bought 22 million new fossil-fueled cars.

'We Haven't Turned the Corner Yet'

Jackson and his colleagues project that emissions will continue to grow next year, as an expanding economy will lead to increasing energy use.

"The main issue is the carbon intensity of global energy production is the same today as it was in 1990," Jackson said.

While a handful of countries have begun to decarbonize their energy systems, by dramatically increasing the use of renewables while also improving efficiency, there's been little progress globally.

"It's shocking in a way," Jackson said. "I believe that wind and solar and renewables will help us turn the corner. We haven't turned the corner yet though."