SACRAMENTO, Calif. — California has set a goal of phasing out electricity produced by fossil fuels by 2045 under legislation signed Monday by Gov. Jerry Brown.

Brown, who has positioned California as a global leader in the effort to reduce greenhouse gas emissions, approved the measure as he prepares to host a summit in San Francisco of climate change leaders from around the world starting Wednesday.

The measure represents the latest in a string of ambitious environmental initiatives as California seeks to fill a void left by President Donald Trump’s decision to withdraw from the Paris climate accord and his efforts to boost the coal industry.

The state is pushing to rapidly expand adoption of electric vehicles and has created a “cap and trade” program to put a price on carbon emissions, creating incentives to reduce them. It’s working toward a goal, pushed by Brown and adopted by lawmakers, to reduce greenhouse gas emissions by 40 percent over the next 12 years.

But the efforts have drawn criticism from business groups worried about rising electric bills. Some environmentalists who say Brown is too cozy with oil and gas interests and plan to disrupt the San Francisco summit.