U.S. greenhouse gas emissions fell 2.1% in 2019 due to a sharp decline in coal consumption, according to preliminary estimates from the independent research firm Rhodium Group.

Rhodium's recently released analysis of both federal and private sector data found that coal-fired power generation fell by a record 18% year on year to the lowest level seen since 1975. The fall in emissions linked to global climate change follows a sharp increase in 2018 as net U.S. greenhouse gas emissions ended 2019 slightly higher than 2016 levels, the group's new report states.

U.S. power generators cut total electricity generation from coal in half in the past decade, authors of the report note. The transition from coal to natural gas and renewable energy sources accounts for much of the progress the country has made to reduce its emissions in the past ten years.

The drop in coal generation reduced greenhouse gas emissions by 190 million metric tons in 2019, the Rhodium Group estimates. A simultaneous rise in natural gas generation offset that reduction by an estimated 40 million metric tons.

Increased natural gas consumption offset some of the declines in coal generation, but overall U.S. power sector emissions still decreased by almost 10% in 2019. The Rhodium Group report found that transportation emissions remained relatively flat while emissions from other parts of the economy rose at a slightly slower rate than in 2018.

"Unfortunately, there was little good news outside the power sector, continuing a trend we have observed for the past several years," the report states.

While efficiency improvements have slowed emissions growth across the economy, it will "require much more than efficiency to achieve meaningful absolute declines" in those sectors, the authors of the report added. While transportation emissions declined slightly by 0.3% year-over-year, industrial emissions rose by 0.6% in the same period. Direct emissions from buildings increased by 2.2% and emissions from other sectors — agriculture, waste, land use and other categories — rose 4.4%.

As the 2020 election season approaches, many expect new climate legislation and a push for other initiatives to lower greenhouse gas emissions to be at the forefront of Democrats' policy work in the coming months. The political party's takeover of the U.S. House of Representatives in 2019 led to several efforts to pass climate change initiatives, including an attempt to keep the U.S. from withdrawing from the Paris Agreement on climate change.