So what’s the catch? It’s this: Things get much, much harder from here on out. California will now have to cut emissions an additional 40 percent by 2030 to keep meeting its climate goals, and that next phase will hurl the state into uncharted territory.

Up until now, California has largely cut emissions by cleaning up its electricity sector. Coal plants have shut down, replaced by natural gas and renewable energy. This is considered the low-hanging fruit of climate policy, aided by the falling costs of wind and solar power, and California has gone further than many other states on this score. (There are roughly as many solar panels installed in the state as the rest of the country combined.)

But greening the electricity sector only gets you so far. Power plants now account for just 16 percent of California’s total emissions (compared with about one-third nationwide). The state will now have to look beyond power plants and address other hard-to-decarbonize parts of the economy.

Transportation, which accounts for 39 percent of the state’s emissions and rising, is going to be the biggest challenge. Californians are driving more with each passing year and stricter fuel economy standards haven’t done enough to offset that. Gov. Jerry Brown has set a goal of putting 5 million zero-emissions vehicles on the road by 2030, but only about 205,000 battery electric and fuel cell vehicles have been sold statewide so far, along with 189,000 plug-in hybrids.

Policymakers have started to go after vehicle emissions more aggressively, adding new gas taxes and funding new charging infrastructure. But trying to change how people drive is proving far more contentious than simply replacing dirtier power plants with cleaner ones. A far-reaching bill that would have promoted denser, transit-oriented development died in the legislature this year. Anti-tax groups are pushing a voter initiative to repeal the gas taxes. And the Trump administration is planning a rollback of federal fuel economy standards, a move that California has vowed to fight.

Elsewhere, the state is also seeking to price carbon emissions, curb methane from dairy cows, clean up its oil refineries and protect its forests in the face of heat and drought. This will require tinkering with largely untested policies and technologies, where the costs are uncertain and success is far from guaranteed.

The rest of the country will be watching closely. Other states have also been making considerable progress in cleaning up their power plants and will soon face the question of what else they should do to cut emissions. As one economist put it to me last fall, California has basically volunteered itself as a “giant laboratory” to test out what works and what doesn’t. No pressure.