State lawmakers and regulators are turning their eyes to the road in the fight against climate change, recognizing that the transportation sector now produces more greenhouse gas emissions than any other portion of the economy.
They are finding few simple solutions.
The Transportation and Climate Initiative released a proposal last month to limit the amount of carbon that fuel suppliers are allowed to emit. The group is made up of 12 Eastern and Mid-Atlantic states plus the District of Columbia, many of which are part of a similar joint effort that has curbed power-sector emissions in the region.
The transportation proposal -- which will require states to opt in before it takes effect -- is off to a much rockier start, with at least one governor already denouncing it.
California, long the leader in policies to curb transportation emissions, also has had trouble advancing its policies. The state is battling the Trump administration in court over its authority to set stricter auto emission levels than the national standard, which the administration rolled back.
Meanwhile, the California Air Resources Board is considering applying its zero-emission car mandate to trucks, ranging from pickups to tractor-trailers. That would require manufacturers to offer electric truck models in California, while meeting certain sales thresholds, the first such mandate in the United States.
Washington Gov. Jay Inslee, a Democrat who has put climate change at the top of his political agenda, recently unveiled three proposals for reducing transportation emissions in the state. But state officials acknowledge the push will be complicated.
"We by and large know what we need to do in the power sector," said Reed Schuler, Inslee's senior policy adviser on climate and sustainability. "The power sector is no one's idea of simple but compared to the transportation sector it is. ... Looking down the road, we know that if we fail to tackle transportation emissions, we will fail to tackle climate change."
Nationwide carbon emissions from the power sector declined 28% between 2005 and 2017, according to the U.S. Energy Information Administration. The decrease was caused by more energy-efficient buildings and lower demand for electricity, as well as a drop in coal production and an increase in adoption of renewable sources.
But transportation emissions rose slowly from 2012 to 2018, and surpassed the power sector for the first time in 2016. Transportation now makes up 29% of national emissions, the U.S. Environmental Protection Agency found.