Over the past decade, California has passed a sweeping set of climate laws to test a contentious theory: that it’s possible to cut greenhouse gas emissions far beyond what any other state has done and still enjoy robust economic growth.

Now that theory faces its biggest test yet. Last August, the State Legislature set a goal of slashing emissions more than 40 percent below today’s levels by 2030, a far deeper cut than President Barack Obama proposed for the entire United States and deeper than most other countries have contemplated.

So how will California pull this off?

On Tuesday, Gov. Jerry Brown signed a new law expanding the state’s cap-and-trade program, which is expected to play a big role. But cutting greenhouse gases this deeply will involve more than cap and trade. The state plans to rethink every corner of its economy, from urban planning to dairy farms.

No one knows yet if it can succeed. “You can think of California as a giant laboratory” for climate action, said Severin Borenstein of the Haas School of Business at the University of California, Berkeley.