The bad is that, as coal fades, some trickier problems are replacing it. As the chart shows, transportation—mostly, gasoline for cars and trucks—is now the biggest source of carbon-dioxide emissions in the United States. CO2 emissions from the transportation sector ticked up 1.9 percent in 2016. But transportation is different from power generation. The mix of electricity sources can be made more climate-friendly by swapping out coal for natural gas and renewables. But reducing emissions from cars and trucks will require less gasoline to be burned, period. So federal fuel-efficiency rules must either get more stringent or there must be a mass consumer move to electric vehicles.

These two factors combine to give the chart above, where CO2 from electric power is steadily falling, but emissions from transportation are slowly rising.

“I really do think that the transition to cleaner energy is underway,” said Carol Werner, the executive director of the Environmental and Energy Study Institute. “There are many factors influencing that, and while the Trump administration is seeking to halt a variety of regulations and policies, I think that there is embedded change. The genie is out of the bottle.”

Obama himself made a similar case in Science in January. “Putting near-term politics aside, the mounting economic and scientific evidence leave me confident that trends toward a clean-energy economy that have emerged during my presidency will continue,” he said.

But the rise in emissions from transportation belies this inevitability. As the price of gasoline falls, people want to drive more and they buy less fuel-efficient vehicles. “With lower gas prices, the sale of SUVs is up,” said Werner. “That is not good.”

These trends could all, of course, change in response to Trump administration policies. The EPA and Department of Transportation have already began to roll back Obama-era policies meant to nudge utilities toward toward building natural-gas, solar, and wind capacity. They have also announced that they will review federal fuel-efficiency standards for cars and light trucks. While these rules have little effect on the price of SUVs, they could lead to gas mileage decreasing nationwide.

The report doesn’t capture all U.S. greenhouse-gas emissions—like methane and hydrofluourocarbons—because some are released through agriculture and other kinds of land use. The government has not yet issued its estimate of total greenhouse-gas emissions for 2016.

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