Emissions goal hit — with one exception

California’s greenhouse gas emissions are falling faster than state leaders hoped when they launched their fight against climate change 12 years ago.

But there’s a glaring exception.

Emissions from transportation — cars, trucks, trains, planes and ships — keep rising. And since transportation accounts for more greenhouse gas emissions than any other sector, that must change if the state hopes to meet its future global warming goals.

Data released last week by the California Air Resources Board show that in 2016, the state’s greenhouse gas emissions passed a major milestone, falling below their levels from 1990. California’s landmark 2006 global warming law called for cutting emissions to 1990’s levels by 2020. In other words, the state reached its goal four years early.

(The board’s process of counting and verifying emissions takes more than a year to complete, so the annual updates are always about 18 months behind.)

But emissions from the transportation sector rose almost 2 percent in 2016. They have increased every year since 2013, as the California economy rebounded from the recession.

And fuel sales data suggest they may increase further in 2017. For all of California’s efforts to promote electric vehicles, the vast majority of the state’s residents still drive vehicles with internal combustion engines. And they’re buying more gas.

“Electric cars are a technology that’s been slow to get mass-shopper appeal,” said Jeremy Acevedo, an analyst with the Edmunds auto information service. “We’ve been waiting for the green car segment to really take off.”

It matters because transportation represents about 39 percent of California’s total emissions (wildfires excepted). State law calls for slashing California’s overall emissions another two-fifths by 2030, a goal that won’t be attainable without significant cuts from transportation. To date, greener electricity, as mandated by the state, has accounted for a significant portion of the emissions reductions; now other economic sectors must find ways to get cleaner too.

“For 2030, our estimates are it’s going to be much more challenging than 2020,” said UC Berkeley energy economist Severin Borenstein. “I’m not sure we’ve plucked much (low-hanging) fruit at all. Look at gasoline consumption — it’s up.”

There have been some significant improvements, although one has to look back over the past decade to see them.

California’s greenhouse gas emissions from transportation peaked at 188.7 million metric tons in 2005. Then they started to slide, as rising gasoline prices prompted consumers to buy more efficient cars or drive less. When the global financial crisis struck in 2008, throwing people out of work and cutting trade, emissions from cars and trucks tumbled.

Now, even though they are rising again, they remain about 10 percent below their peak. That’s due in large part to tougher fuel-efficiency standards that California imposed on automakers in 2002 and that President Obama took nationwide in 2009.

The Trump administration, which has worked to suspend or roll back Obama’s climate initiatives, now wants to do the same with cars, halting further federal mileage improvement requirements after 2021. It is also contemplating trying to revoke California’s legal right to set its own air-pollution standards for cars, which could affect the state’s fuel-economy rules.

The outcome is far from certain. Automakers, which asked Trump for flexibility on the mileage requirements shortly after his election, have balked at the possibility of another long legal battle between California and the federal government. And some of them are planning to dramatically expand their production of electric vehicles.

“While they want more flexibility, they don’t want to stop the improvements in fuel economy,” said Chris Busch, research director for the Energy Innovation consulting firm.

California has pushed hard, for years, to get more zero-emission vehicles on the road. The state offers financial incentives for cars running on batteries or fuel cells, as well as a highly coveted perk — a sticker that lets the car’s owner drive solo in carpool lanes, though these stickers expire after several years.

The greenhouse gas savings that electric cars represent varies from one state to another, depending on the mix of electricity sources feeding the local power grid. In California, it’s huge.

The state last year derived 29 percent of its electricity from renewable sources, according to the California Energy Commission, while large hydroelectric dams — which are counted separately — provided nearly 15 percent.

A study this spring by the Union of Concerned Scientists, a nonprofit research group, found that the average electric car in California had the same emissions as a gasoline-powered car getting 109 miles per gallon, when the sources of the state’s electricity supply were taken into account. The most efficient electric cars produced the same emissions as a 147-mpg gasoline car. And those figures should improve as California keeps ramping up its use of renewable power.

“We’re replacing fossil fuels with wind and solar, and with greening up transportation, those things go hand-in-hand,” said David Reichmuth, a senior engineer in the union’s clean vehicles program. “The interesting thing about an electric vehicle is, you buy it, and it can get cleaner over time, because the electric mix gets cleaner over time.”

But fewer Californians are buying electric vehicles than the state might like.

Although California is by far the country’s largest EV market, accounting for over half of all sales nationwide, just 202,184 have been registered in the state. California also has 188,997 plug-in hybrids, according to a registration-tracking website sponsored by the Alliance of Automobile Manufacturers lobbying group. Gov. Jerry Brown has set a goal of having 5 million emissions-free vehicles on California roads by 2030, and the state is taking a number of actions — from adding fees to gasoline sales to boosting charging infrastructure — in an effort to pry people away from conventional cars.

Promisingly for the state, the range of electric vehicles continues to improve, though they remain generally more expensive than gasoline-powered cars. The all-electric Chevy Bolt, for example, can go 238 miles on a fully charged battery. It was the most popular electric car in California last year, with 13,487 registered within the state. Tesla’s Model S and Model 3 can also go over 200 miles before needing to charge.

“At 200 miles, I know I won’t be tethered to my house,” Acevedo said.

Still, the percentage of buyers remains small. So far this year, pure electric cars account for 3 percent of new registrations in the state, while plug-in hybrids account for another 3 percent, Acevedo said, citing figures from the IHS Markit research firm.

Acevedo also sees potential in Tesla’s new Model 3. Although the Palo Alto company has struggled to ramp up production and not yet even produced the $35,000 version that is billed as having mass-market appeal, 420,000 people worldwide hold reservations for the car.

“It’s a huge number, and it could really move the needle,” Acevedo said. “Tesla’s one of those automakers that has the ability to garner consumer attention.”

David R. Baker is a San Francisco Chronicle staff writer. Email: dbaker@sfchronicle.com Twitter: @DavidBakerSF