(CNN) After three years of decline, climate-change-causing carbon emissions rose sharply in the United States last year, according to new research.
Carbon emissions increased 3.4% in 2018, marking the second-largest annual gain in more than two decades, according to preliminary power generation data analyzed by the Rhodium Group, an independent economic policy research provider.
This follows a Global Carbon Project report in December that said global carbon emissions were estimated to rise by 2.7% for all of 2018.
The new research indicated that US power sector emissions as a whole rose by 1.9% and that the transportation sector "held its title as the largest source of US emissions for the third year running," due to a growth in demand for diesel and jet fuel offsetting a modest decline in gasoline use.
The construction and industry sectors also saw sizable emission increases.
"Most of the increase last year was directly attributable to an increase in economic growth," said Trevor Houser, who leads Rhodium Group's Energy and Climate team, but he added that "it does not have to be the case that a rising economy results in rising emissions."
Houser said affordable technology exists to grow the economy while reducing emissions, "but that requires policy to deploy those technologies in the market. And we've seen a freeze in that kind of policy at the federal level over the past few years."
The lack of strategy in the country's decarbonization efforts, the research says, has contributed to the gap in meeting the goal set in the Paris Agreement on climate change, a landmark 2015 accord that the US Trump administration has promised to abandon.
President Trump has at times denied the basic science of climate change, which states that burning coal, oil and natural gas produces emissions that trap heat in the atmosphere, warming the planet. But it has become increasingly clear that warming is happening faster than previously thought and with worse results.
In November, the administration released its fourth national climate assessment outlining the dire environmental and economic impacts of climate change, stating that thousands of Americans could die and gross domestic product could take a 10% hit by century's end.
Trump, who has called climate change a "hoax," has rejected the report's conclusion that climate change could be devastating for the economy, saying, "I don't believe it."
His administration has since made a series of policy and diplomatic decisions or statements that appear to run counter to all of the warnings in the report. None is designed to reduce fossil fuel emissions, as the report said is needed to combat extreme climate change.
In December, the Environmental Protection Agency proposed relaxing regulations for newly built coal-fueled power plants, which, combined with another proposal to replace the Obama-era Clean Power Plan, would overhaul the way coal-fired plants are built and regulated.
The move sent a political signal that the Trump administration is intent on shoring up the coal industry and other energy interests, and environmentalists worry that the proposed rule suggests the EPA will set new standards that would weaken the requirements that the agency uses to regulate other types of pollution.
At the G20 meeting in Argentina, just days after the release of that dire climate report, US diplomats insisted on noting that the United States reaffirmed its intention to withdraw from the Paris accord.
When the US Geological Survey announced a major discovery of oil and natural gas underneath Texas and New Mexico in December, Interior Secretary Ryan Zinke called it a gift.
The Interior Department then proposed to cut protections that benefited the sage grouse, a grassland bird that lives in the Great Plains and Western states, which could allow for expanded oil and drilling. The plan would remove protections on nearly 9 million acres of protected habitat.