No matter that coal-fired power plants went out of business in record numbers, or that Americans nearly doubled their purchases of electric cars. The U.S. increased its carbon dioxide emissions in 2018, and a large part of the reason was one normally cited as a bonus — substantial economic growth.

A booming American economy meant increased industrial production, more truck and air travel and more offices and other workplaces to heat — all combining, along with other factors, to create the second-largest annual increase in the key greenhouse gas emissions in more than two decades, according to new estimates from the Rhodium Group.

The result is that — despite expansion of solar and wind power and some movement to alternative-fuel vehicles — the U.S. will have to do even more in the coming years to come close to meeting previous international commitments for greenhouse gas reductions.

“We know that CO2 comes from things like burning fuel for manufacturing and burning coal to produce steel and burning gas to move cars and trucks,” said José Tapia Granados, an economist at Drexel University in Philadelphia, who has done research on the impact of economic growth on global warming. “All this economic activity produces carbon dioxide, and money for somebody. So emissions tend to be greater in periods of greater economic activity.”

Carbon dioxide is the most common greenhouse gas, and excess emissions concern scientists because they trap heat in Earth’s atmosphere, driving up temperatures and triggering a cascading series of problems — from droughts and mega-storms to more intense wildfires, like those that charred broad swaths of California in 2018.

America's greenhouse gas emissions hit their peak in 2007, just before the economic meltdown, with all sectors combining to release 6 billion metric tons of carbon dioxide. Emissions continued on a generally downward tilt through 2017, when they dropped to 5.14 billion tons. But the rate of decline slowed significantly in recent years, as the economy rebounded.

And the new report projects an increase to 5.32 billion metric tons of CO2 in 2018. That is 3.4 percent higher than those in 2017, the second largest increase in more than two decades and the biggest jump since 2010, when the American economy began to rebound from the Great Recession.

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The report emphasizes that the numbers are preliminary estimates, with the Environmental Protection Agency scheduled to release actual figures in 2020.

The early estimates reinforce the sense that the U.S. faces a steep challenge in trying to rein in greenhouse gas emissions that are second only to China’s.

Efforts to decrease the amount of carbon dioxide spewing into the atmosphere were challenging in every economic sector, including:

• Electrical power, where shuttered coal-fired power plants helped to ameliorate emissions increases, but not as much as scientists had hoped. That is because the healthy economy and a severe cold snap in the Northeast drove up demand for heating and cooking fuel. And much of that power came from natural gas-burning power plants. While gas facilities release less CO2 than coal-fueled plants, they are not as clean as zero-emissions solar and wind farms. As a result, power sector emissions rose by 1.9 percent.

• Transportation, where a boom in the sale of electrical cars — from just under 200,000 in 2017 to more than 361,000 in 2018 — helped reduce gasoline consumption slightly. But that decline was more than reversed — and emissions driven upward — by the jump in truck and jet fuel consumption, which both grew by about 3 percent.

“This highlights the challenges in decarbonizing the transportation sector beyond light-duty vehicles,” the Rhodium report said.

• Buildings, which saw emissions increase 10 percent, to the highest level since 2004. That CO2 comes from burning fuel oil, diesel and natural gas for heating and cooking. Part of the jump is explained by an unusually cold winter in 2018, but the report’s authors said more work needs to be done to improve energy efficiency. It called buildings one of the sectors “most often ignored in clean energy and climate policymaking.”

• Industry produced the largest gain of any sector ― more than 55 million additional metric tons of carbon dioxide, compared to the year prior. Much of the jump came courtesy of a high-revving economy, the report said, as exemplified by an increase of 7.3 percent in all sorts of manufacturing shipments during the first nine months of the year.

“Absent a significant change in policy or a major technological breakthrough, we expect the industrial sector to become an increasingly large share of U.S. greenhouse gas emissions in the years ahead, including non-CO2 gases,” the Rhodium report said. “We expect it to overtake power as the second leading source of emissions in California by 2020 and to become the leading source of emissions in Texas by 2022.”

Drexel’s Tapia Granados co-authored a study in 2012 which found that, from 1958 through 2010, CO2 emissions were closely linked to increased economic activity.

“It's a message no one wants to hear: to slow down global warming, we'll either have to put the brakes on economic growth or transform the way the world's economies work,” a summary of the study said.

"If 'business as usual' conditions continue, economic contractions the size of the Great Recession or even bigger will be needed to reduce atmospheric levels of CO2," Tapia Granados said at the time of the paper’s release.

The failure of the U.S. and other nations to make more progress is particularly striking, given that the U.N. officially recognized the challenge of excess carbon dioxide at least as far back as a 1992 climate convention, said Mathis Wackernagel, president of the climate think tank Global Footprint Network.

"Today, even the percentage of energy coming from fossil fuels is higher than back then," said Wackernagel. "That is in spite of all the [technological] advances in photovoltaic cells and the like. And the intention to do more."

Indeed, the Rhodium report suggests that greenhouse gas emissions dipped with the recession and will now keep increasing, without serious shifts in policy and behavior.

The new study “highlights the limited progress made in developing decarbonization strategies for these sectors.” This news comes as the U.S. is already struggling to meet its commitments under the 2015 Paris climate agreement. The report concludes: “The gap is even wider headed into 2019.”