The Rhodium Group, an independent research provider, estimates that, after a sharp uptick in 2018, US greenhouse gas (GHG) emissions fell by 2.1% in 2019 based on preliminary energy and economic data. This decline was due almost entirely to a drop in coal consumption.

Coal-fired power generation fell by a record 18% year-on-year to its lowest level since 1975. An increase in natural gas generation offset some of the climate gains from this coal decline, but overall power sector emissions still decreased by almost 10%.

Far less progress was made in other sectors of the economy. Transportation emissions remained relatively flat. Emissions from buildings, industry and other parts of the economy rose, though less than in 2018. All told, net US GHG emissions ended 2019 slightly higher than at the end of 2016.

At roughly 12% below 2005 levels, the US is at risk of missing its Copenhagen Accord target of a 17% reduction by the end of 2020, and is still a long way off from the 26-28% reduction by 2025 pledged under the Paris Agreement.

Coal-driven decline. The switch from coal to natural gas and renewables in the electric power sector accounts for the majority of the progress the US has made in reducing emissions over the past decade. This was particularly true last year. Based on a combination of monthly data from the Energy Information Administration and daily data from Genscape, Rhodium estimates that coal-fired power generation fell by 18% in 2019.

That’s the largest year-on-year decline in recorded history with coal generation now at its lowest level since 1975. It also marks the end of a decade in which total US coal generation was cut in half.

Natural gas generation made up much of the gap last year, as it has consistently in recent years, due to extremely cheap gas prices. Average annual prices at Henry Hub were down 20% in 2019, adjusted for inflation, to their lowest level in decades. Renewables played an important role as well thanks in part to continued cost declines in both wind and solar generation. Based on preliminary data from EIA and Genscape, utility-scale renewable generation (including hydro) was up 6% in 2019. That’s higher than the 3% gain in 2018, but lower than the 13% gains posted in 2016 and 2017.

The drop in coal generation reduced emissions by 190 million metric tons in 2019. The growth in gas generation shaved a little more than 40 million metric tons off this number. But electric power sector emissions were still down by nearly 10%—the biggest year-on-year drop in decades, and a significant change from a 1.2% increase in 2018.

Transportation. Based on preliminary data, Rhodium estimates that transportation emissions declined slightly—by 0.3% year-on-year. Industrial emissions (both energy and process) rose by 0.6%. Direct emissions from buildings increased by 2.2% and emissions from other sectors (agriculture, waste, land use, oil and gas methane, etc) rose by 4.4%.

In the transportation sector, domestic air travel grew by 2.3% year-on-year in the first three quarters of 2019, compared to 4.1% during the same period in 2018. As a result, jet fuel demand growth slowed from 2.6% to 1.8% during the first three quarters of 2019.

Growth in the amount of freight moved by truck slowed from 7.1% year-on-year during the first three quarters of 2018 to 4.1% during the same period in 2019. That turned a 5.6% increase in year-on-year diesel demand during the first three quarters in 2018 to a 0.8% decline during the same period in 2019.

Improvements in vehicle, lighting, and appliance efficiency have been successful in slowing the pace of emissions growth in transportation and buildings (and perhaps even halting it in transportation), Rhodium said, but it will require much more than efficiency to achieve meaningful absolute declines. Large-scale fuel substitution (to decarbonized electricity and other zero-carbon fuels) will be required. States have some ability to drive this in absence of federal policy action.