Senator Bernie Sanders on Thursday released a $16.3 trillion blueprint to fight climate change, the latest and most expensive proposal from the field of Democratic presidential candidates aimed at reining in planet-warming greenhouse gases.

Mr. Sanders unveiled his proposal one day after Gov. Jay Inslee of Washington, who made climate change the central focus of his campaign, announced he was dropping out of the 2020 race. Mr. Inslee’s absence could create an opening for another presidential aspirant to seize the mantle of “climate candidate.”

Mr. Sanders was an early supporter of the Green New Deal, an ambitious but nonbinding congressional plan for tackling global warming and economic inequality. He is bestowing that same name upon his new plan, which calls for the United States to eliminate fossil fuel use by 2050.

It declares climate change a national emergency; envisions building new solar, wind and geothermal power sources across the country; and commits $200 billion to help poor nations cope with climate change.